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MBA Operations Management - Test Bank - Chapter 15

MBA Operations Management

Operations Management, 12e (Heizer/Render/Munson)

Chapter 15  Short-Term Scheduling 

Section 1   The Importance of Short-Term Scheduling

 

1) Alaska Airlines uses mathematical short-term scheduling techniques and a high-tech nerve center to manage the rapid rescheduling necessary to cope with weather delays and similar disruptions.

Answer:  TRUE

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

2) Short-term scheduling is important to efficiency and to cost reduction, but its impact is not of strategic importance.

Answer:  FALSE

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

3) The benefits of effective scheduling include lower cost, faster throughput, and dependable delivery.

Answer:  TRUE

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

4) Which of the following statements regarding scheduling at Alaska Airlines is FALSE?

  1. A) Flying into Alaska complicates scheduling.
  2. B) Schedule changes at one airport have a ripple effect that may have impacts in many others.
  3. C) Alaska Airlines' high-tech computer and communications system is located in Seattle.
  4. D) Alaska Airlines' rapid rescheduling uses mathematical scheduling models.
  5. E) Alaska Airlines' rapid rescheduling promotes air safety and limits traveler inconvenience, but has not resulted in money savings for Alaska Airlines.

Answer:  E

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

5) Which of the following is NOT a key direct benefit from effective internal or external scheduling?

  1. A) lower cost
  2. B) greater use of assets
  3. C) more dependable delivery
  4. D) higher quality
  5. E) added flexibility

 

Answer:  D

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

6) Briefly describe how "the unexpected" makes short-term scheduling at Alaska Airlines a challenge. Also describe how Alaska Airlines meets that challenge, and achieves competitive advantage through short-term scheduling.

Answer:  The unexpected refers to delays and cancellations that are largely weather-related. These events require rapid rescheduling in order to keep operations going and to keep passengers from becoming too inconvenienced. Alaska Airlines' solution involves a high-tech nerve center of computers and communications gear, and it uses mathematical models to reroute and reschedule as quickly as possible.

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

7) What makes short-term scheduling of strategic importance?

Answer: 

  1. Internally effective scheduling means faster movement of goods and services through a facility and greater use of assets. The result is greater capacity per dollar invested, which translates into lower costs.
  2. Externally good scheduling provides faster throughput, added flexibility, and more dependable delivery, improving customer service.

Diff: 3

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

Section 2   Scheduling Issues

 

1) With forward scheduling, jobs are scheduled as late as possible within the time allowed by the customer due dates.

Answer:  FALSE

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

2) One criterion for developing effective schedules is minimizing completion time.

Answer:  TRUE

Diff: 1

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

3) Process-focused facilities and repetitive facilities generate forward-looking schedules, but process-focused facilities do this with JIT and kanban while repetitive facilities generally use MRP.

Answer:  FALSE

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

4) What is the objective of scheduling?

  1. A) maximize quality
  2. B) minimize cost
  3. C) minimize response time
  4. D) prioritize and allocate demand to available facilities
  5. E) minimize lead time

Answer:  D

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

5) The correct sequence from longest to smallest duration scheduling is:

  1. A) capacity planning, aggregate planning, master schedule, short-term scheduling.
  2. B) aggregate planning, capacity planning, master schedule, short-term scheduling.
  3. C) master schedule, capacity planning, aggregate planning, short-term scheduling.
  4. D) master schedule, aggregate planning, capacity planning, short-term scheduling.
  5. E) capacity planning, master schedule, aggregate planning, short-term scheduling.

Answer:  A

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

6) Forward scheduling is the scheduling of:

  1. A) the end items or finished products.
  2. B) jobs as soon as the requirements are known.
  3. C) the start items or component parts.
  4. D) the final operation first beginning with the due date.
  5. E) jobs according to their profit contributions.

Answer:  B

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

7) Short-term schedules are prepared:

  1. A) directly from the aggregate plans.
  2. B) directly from the capacity plans.
  3. C) from inventory records for items that have been used up.
  4. D) from master schedules, which are derived from aggregate plans.
  5. E) from the purchasing plans.

Answer:  D

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

8) Which of the following is not an effectiveness criterion for scheduling?

  1. A) minimizing customer waiting time
  2. B) minimizing completion time
  3. C) minimizing WIP inventory
  4. D) maximizing utilization
  5. E) maximizing flow time

Answer:  E

Diff: 1

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

9) Which of the following considers process capacity when scheduling?

  1. A) cap loading
  2. B) constrained loading
  3. C) capacitated loading
  4. D) backward loading
  5. E) finite loading

Answer:  E

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

10) Forward scheduling:

  1. A) begins with a delivery date, then offsets each operation one at a time, in reverse order.
  2. B) has the same meaning as "finite loading."
  3. C) is often used in service environments such as catering a banquet or scheduling surgery.
  4. D) starts the schedule as soon as the job requirements are known.
  5. E) produces a schedule only if it meets the due date.

Answer:  D

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

11) The short-term scheduling activity called "loading":

  1. A) assigns dates to specific jobs or operations steps.
  2. B) specifies the order in which jobs should be done at each center.
  3. C) assigns jobs to work centers
  4. D) assigns workers to jobs.
  5. E) assigns workers to machines.

Answer:  C

Diff: 2

Key Term:  Loading jobs

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

12) ________ scheduling begins with the due date and schedules the final operation first and the other job steps in reverse order.

Answer:  Backward

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

13) In the sequence of decisions that affect scheduling, ________ is (are) the immediate follower(s) of the master schedule (or master production schedule).

Answer:  short-term schedules

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

14) ________ is the assignment of jobs to work or processing centers.

Answer:  Loading

Diff: 2

Key Term:  Loading

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

15) Explain, in your own words, how backward scheduling and forward scheduling differ.

Answer:  Forward scheduling starts the schedule as soon as the requirements are known. Backward scheduling begins with the due date, scheduling the final operation first and proceeding in the reverse order.

Diff: 2

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

16) Compare short-term scheduling at process-focused, repetitive, and product-focused facilities.

Answer:  Process-focused: (1) Scheduling to customer orders where changes in both volume and variety of jobs/clients/patients are frequent. (2) Schedules are often due-date focused, with loading refined by finite loading techniques.

Repetitive: (1) Schedule module production and product assembly based on frequent forecasts. (2) Finite loading with a focus on generating a forward-looking schedule. (3) JIT techniques are used to schedule components that feed the assembly line.

Product-focused: (1) Schedule with high-volume finished products of limited variety to meet a reasonably stable demand within existing fixed capacity. (2) Finite loading with a focus on generating a forward-looking schedule that can meet known setup and run times for the limited range of products.

Diff: 3

Objective:  LO 15.1 Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

Section 3   Scheduling Process-Focused Facilities

 

1) Which of the following is NOT required to be known in order to schedule process-focused facilities?

  1. A) the sequence of work
  2. B) which workers are assigned to each work center
  3. C) the time required for each item
  4. D) the capacity of each work center
  5. E) the availability of each work center

Answer:  B

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

Section 4   Loading Jobs

 

1) The constant work-in-process (ConWIP) card aids input-output control by limiting the amount of work in a work center.

Answer:  TRUE

Diff: 1

Key Term:  ConWIP cards

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

2) A Gantt load chart shows the loading and idle time of several departments, machines, or facilities.

Answer:  TRUE

Diff: 2

Key Term:  Gantt charts

Objective:  LO 15.2 Draw Gantt loading and scheduling charts

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

3) Gantt charts are useful for scheduling jobs, but not for loading them.

Answer:  FALSE

Diff: 1

Key Term:  Gantt charts

Objective:  LO 15.2 Draw Gantt loading and scheduling charts

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

4) The assignment method provides an optimum, one-to-one assignment of jobs to resources.

Answer:  TRUE

Diff: 1

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

5) A work center had actual input of 280 hours and actual output of 270 hours. What is the change in backlog?

  1. A) 10
  2. B) -10
  3. C) 0
  4. D) 1.037
  5. E) Unable to determine with the given information

Answer:  A

Diff: 2

Key Term:  Input-output control

AACSB:  Analytical thinking

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

6) A work center had planned outputs of 10, 15, 13, and 20 hours with actual outputs of 12, 14, 13, and 18 hours. What is the cumulative deviation in output?

  1. A) 0
  2. B) 1
  3. C) -1
  4. D) 58
  5. E) Unable to determine with the given information

Answer:  C

Diff: 2

Key Term:  Input-output control

AACSB:  Analytical thinking

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

7) A work center is interested in limiting work-in-process by not allowing production to start again until the current batch is finished. The best solution most likely involves:

  1. A) MRP.
  2. B) ConWIP cards.
  3. C) Gantt charts.
  4. D) Johnson's rule.
  5. E) the assignment method.

Answer:  B

Diff: 2

Key Term:  ConWIP cards

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

8) The assignment method is:

  1. A) a method to highlight overloads in a given work center.
  2. B) a computerized method of determining appropriate tasks for an operation.
  3. C) a form of linear programming for optimally assigning tasks or jobs to resources.
  4. D) the same thing as the Gantt schedule chart.
  5. E) a method for achieving a balance between forward and backward scheduling.

Answer:  C

Diff: 2

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

9) What is a scheduling technique used to achieve an optimum, one-to-one matching of tasks and resources?

  1. A) the assignment method
  2. B) Johnson's rule
  3. C) the CDS algorithm
  4. D) the appointment method
  5. E) the reservation method

Answer:  A

Diff: 2

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

10) There are two jobs to be assigned to two workers. The profit for worker A on job 1 is $5 and on job 2 is $8. The profit for worker B on job 1 is $10 and on job 2 is $12. How should the work be divided using the assignment method?

  1. A) worker A assigned to job 1 and worker B assigned to job 2
  2. B) worker A assigned to job 2 and worker B assigned to job 1
  3. C) worker A gets both jobs 1 and 2
  4. D) worker B gets both jobs 1 and 2
  5. E) unable to determine

Answer:  B

Diff: 2

Key Term:  Assignment method

AACSB:  Analytical thinking

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

11) If job 5 takes 3, 4 or 5 hours to be completed by workers A, B, and C, respectively, what would the row values for job 5 be after performing Step 1A of the assignment method?

  1. A) 3, 4, 5
  2. B) 8, 9, 10
  3. C) 0, 1, 2
  4. D) 6, 7, 8
  5. E) 1, 4/3, 5/3

Answer:  C

Diff: 2

Key Term:  Assignment method

AACSB:  Analytical thinking

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

12) Which of the following is an aid used to monitor jobs in progress?

  1. A) a Gantt load chart
  2. B) the assignment method
  3. C) a Gantt schedule chart
  4. D) Johnson's rule
  5. E) a Gantt progress chart

Answer:  C

Diff: 2

Key Term:  Gantt charts

Objective:  LO 15.2 Draw Gantt loading and scheduling charts

Learning Outcome:  Describe the stages of short-term and long-term scheduling

13) What is a method of input-output control that uses a system of cards to limit the amount of work at a work center and also to control lead time and monitor backlog?

  1. A) the assignment method
  2. B) backward scheduling
  3. C) forward scheduling
  4. D) ConWIP cards
  5. E) level material use

Answer:  D

Diff: 2

Key Term:  ConWIP cards

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

14) If an assignment problem consists of 6 workers and 7 projects:

  1. A) one worker will not get a project assignment.
  2. B) one worker will be assigned two projects.
  3. C) each worker will contribute work toward the seventh project.
  4. D) one project will not get a worker assigned.
  5. E) The problem cannot be solved by assignment method.

Answer:  D

Diff: 2

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

15) If an assignment problem consists of 5 workers and 4 projects:

  1. A) one worker will not get a project assignment.
  2. B) one project will be assigned two workers.
  3. C) the fifth worker will split time among the four projects.
  4. D) one project will not get a worker assigned.
  5. E) The problem cannot be solved by assignment method.

Answer:  A

Diff: 2

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

16) Three jobs are to be assigned to three machines. Cost for each job-machine combination appears in the table below. Perform the first two steps of the assignment method (subtract the smallest number in each row and subtract the smallest number in each column; then cover with straight lines). At this point in the problem-solving process:

 

 

Machine A

Machine B

Machine C

Job 1

11

14

6

Job 2

8

10

11

Job 3

9

12

7

 

  1. A) the row for Job 1 contains the values 5, 6, and 0.
  2. B) calculations are complete, and the problem is ready for an optimal set of assignments.
  3. C) the column for Machine B indicates that it should be retired.
  4. D) Job 1 should be performed on Machine B.
  5. E) Job 1 should be performed on Machine A.

Answer:  A

Diff: 3

Key Term:  Assignment method

AACSB:  Analytical thinking

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

17) ________ cards are used to control the amount of work in a work center, aiding input-output control.

Answer:  ConWIP or Continuous work-in-process

Diff: 2

Key Term:  ConWIP cards

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

18) ________ are planning charts used to schedule resources and allocate time.

Answer:  Gantt charts

Diff: 2

Key Term:  Gantt charts

Objective:  LO 15.2 Draw Gantt loading and scheduling charts

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

19) The ________ is a special class of linear programming models that involves assigning tasks or jobs to resources.

Answer:  assignment method

Diff: 2

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

20) What is input-output control?

Answer:  Input-output control is a technique that allows operations personnel to manage facility work flow by tracking work added to a work center and its completed work.

Diff: 2

Key Term:  Input-output control

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

21) What is the assignment method?

Answer:  The assignment method is a special class of linear programming models that involves assigning tasks or jobs to resources.

Diff: 2

Key Term:  Assignment method

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

22) Identify the major disadvantages of the Gantt load chart.

Answer:  It does not account for production variability, such as unexpected breakdowns or human errors that require reworking a job. Consequently, the chart must be updated regularly to account for new jobs and revised time estimates.

Diff: 2

Key Term:  Gantt charts

Objective:  LO 15.2 Draw Gantt loading and scheduling charts

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

23) What is the difference between a Gantt load chart and a Gantt scheduling chart?

Answer:  The Gantt load chart indicates a planned allocation of capacity–the allocation of the capacity of a department or work center to a particular job or order. The Gantt schedule chart is used to monitor jobs in progress. It indicates which jobs are on schedule and which are ahead of or behind schedule.

Diff: 2

Key Term:  Gantt charts

Objective:  LO 15.2 Draw Gantt loading and scheduling charts

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

24) The president of a consulting firm wants to minimize the total number of hours it will take to complete four projects for a new client. Accordingly, she has estimated the time it should take for each of her top consultants—Charlie, Gerald, Johnny, and Rick—to complete any of the four projects, as follows:

 

Project Hours

Consultant

A

B

C

D

Charlie

13

16

11

18

Gerald

13

15

10

12

Johnny

15

11

20

15

Rick

17

17

12

22

 

(a)  What is the total number of hours required by the following arbitrary assignment?

Charlie→B; Gerald→A; Johnny→D; Rick→C

(b)  What is the optimal assignment of consultants to projects? (Use the assignment method.)

(c)   For the optimal schedule, what is the total number of hours it will take these consultants to complete these projects?

Answer:  (a) 16 + 13 + 15 + 12 = 56 hours (b) The table appears below. (c) 48 hours.

 

 

Project A

Project B

Project C

Project D

Charlie

1

0

0

0

Gerald

0

0

0

1

Johnny

0

1

0

0

Rick

0

0

1

0

 

Diff: 3

Key Term:  Assignment method

AACSB:  Analytical thinking

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

25) Lockport Marine Services, Inc. wishes to assign a set of jobs to a set of machines. The following table provides data on the cost of production of each job when performed on a specific machine.

(a) Determine the set of assignments that minimizes production cost.

(b) What is the total production cost of your assignments?

 

 

Machine

Job

A

B

C

D

1

27

29

28

30

2

30

29

27

26

3

31

25

29

26

4

29

31

25

28

 

Answer:  (a) The optimal set of assignments is Job 1→Machine A, Job 2→Machine D, Job 3→Machine B, and Job 4→Machine C. (b) The total production cost is 27 + 26 + 25 + 25 = 103.

Diff: 3

Key Term:  Assignment method

AACSB:  Analytical thinking

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

26) Machines A, B, C, and D have been in use for several years, while machine E is new. The following table provides data on the value of production of each job when performed on a specific machine.

(a) Determine the set of assignments that maximizes production value.

(b) What is the total production value of your assignments?

(c) Which machine should be retired (i.e., gets no assignment)?

 

 

Machine

Job

A

B

C

D

E

1

27

29

28

30

40

2

30

32

31

34

46

3

33

25

29

26

37

4

29

31

24

28

28

 

Answer:  NOTE: students need to create an opportunity loss table with a dummy Job row. (a) The optimal assignment is Job 1→D, Job 2→E, Job 3→A, and Job 4→B. (b) The value of this assignment is 140. (c) C gets no assignment, and should be the machine retired.

Diff: 3

Key Term:  Assignment method

AACSB:  Analytical thinking

Objective:  LO 15.3 Apply the assignment method for loading jobs

Learning Outcome:  Describe the stages of short-term and long-term scheduling

Section 5   Sequencing Jobs

 

1) Earliest due date is a shop floor dispatching (sequencing) rule that relates the time available to complete a job to the amount of work left to be completed.

Answer:  FALSE

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

2) The critical ratio sequencing rule prioritizes the jobs based on the importance or value of the customers who have placed the orders.

Answer:  FALSE

Diff: 2

Key Term:  Critical ratio (CR)

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

3) Dispatching rules are typically judged by four effectiveness criteria: average completion time, utilization, average number of jobs in the system, and average job lateness.

Answer:  TRUE

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

4) Johnson's rule sequences a set of jobs through two different machines or work centers in the same order.

Answer:  TRUE

Diff: 2

Key Term:  Johnson's rule

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

5) The jobs listed below need to be completed. Assume that it is now day 140. If the jobs are sequenced according to the longest processing time rule, what is the lateness of job A?

 

Job

Processing Time (days)

Job due date (days)

A

20

180

B

30

200

C

10

175

D

16

230

E

18

210

 

  1. A) 0.0 days
  2. B) 24.0 days
  3. C) 7.4 days
  4. D) 9.0 days
  5. E) 11.6 days

Answer:  D

Diff: 2

Key Term:  Priority rules

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

6) The jobs listed below need to be completed. Assume that it is now day 140. If the jobs are sequenced according to the shortest processing time rule, what is the average completion time?

 

Job

Processing Time (days)

Job due date (days)

A

20

180

B

30

200

C

10

175

D

16

230

E

18

210

 

  1. A) 47.6 days
  2. B) 60.2 days
  3. C) 94.0 days
  4. D) 2.5 days
  5. E) 238.0 days

Answer:  A

Diff: 2

Key Term:  Priority rules

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

7) EDD stands for what?

  1. A) earliest due date
  2. B) earliest design date
  3. C) earliest detrimental date
  4. D) earliest decision date
  5. E) economic date determination

Answer:  A

Diff: 1

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

8) Using LPT priority would result in what sequence for Jobs A, B, C, and D if their process times are 4, 6, 5, and 2 respectively?

  1. A) ABCD
  2. B) DCBA
  3. C) DACB
  4. D) DABC
  5. E) BCAD

Answer:  E

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

9) Orders are processed in the sequence in which they arrive if (the) ________ rule sequences the jobs.

  1. A) earliest due date
  2. B) slack time remaining
  3. C) first come, first served
  4. D) critical ratio
  5. E) Johnson's

Answer:  C

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

10) Which of the following dispatching rules ordinarily gives the best results when the criterion is quickest time for completion of the full sequence of jobs?

  1. A) shortest processing time (SPT)
  2. B) critical ratio (CR)
  3. C) first in, first out (FIFO)
  4. D) first come, first served (FCFS)
  5. E) longest processing time (LPT)

Answer:  A

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

11) Five jobs are waiting to be processed. Their processing times and due dates are given below. Using the shortest processing time dispatching rule, in which order should the jobs be processed?

 

Job

Processing Time (days)

Job due date (days)

A

4

7

B

7

4

C

8

11

D

3

5

E

5

8

 

  1. A) A, B, C, D, E
  2. B) C, E, A, D, B
  3. C) B, D, A, E, C
  4. D) D, A, E, B, C
  5. E) C, E, A, B, D

Answer:  D

Diff: 1

Key Term:  Priority rules

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

12) Sequencing (or dispatching):

  1. A) assigns dates to specific jobs or operations steps.
  2. B) assigns jobs to work centers.
  3. C) specifies the order in which jobs should be done at each center.
  4. D) assigns workers to jobs.
  5. E) assigns workers to machines.

Answer:  C

Diff: 2

Key Term:  Sequencing

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

13) Five jobs are waiting to be processed. Their processing times and due dates are given below. Using the earliest due date dispatching rule, in which order should the jobs be processed?

 

Job

Processing Time (days)

Job due date (days)

A

4

7

B

2

4

C

8

11

D

3

5

E

5

8

 

  1. A) C, E, A, D, B
  2. B) A, B, C, D, E
  3. C) B, D, A, E, C
  4. D) C, B, A, E, D
  5. E) B, D, A, C, E

Answer:  C

Diff: 1

Key Term:  Priority rules

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

14) Flow time represents the time:

  1. A) an order spends waiting for processing at a work center.
  2. B) an order spends being processed at a work center.
  3. C) an order spends moving from one work center to another.
  4. D) to complete an order, including time spent in processing and in waiting.
  5. E) none of the above

Answer:  D

Diff: 2

Key Term:  Sequencing jobs

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

15) Which of the following dispatching rules tends to minimize job flow time?

  1. A) FCFS: first come, first served
  2. B) SPT: shortest processing time
  3. C) EDD: earliest due date
  4. D) LPT: longest processing time
  5. E) FCLS: first come, last served

Answer:  B

Diff: 2

Key Term:  Flow time

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

16) Average completion time for a schedule sequence at a work center is the ratio of:

  1. A) total processing time to the number of jobs.
  2. B) total flow time to total processing time.
  3. C) total flow time to the number of jobs.
  4. D) total processing time plus total late time to the number of jobs.
  5. E) total flow time plus total late time to the number of jobs.

Answer:  C

Diff: 2

Key Term:  Sequencing

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

17) Eight jobs have been sequenced at a single work center. Total processing time for the eight jobs is 34 hours, and total flow time for the sequence is 85 hours. For this schedule, utilization is ________ and the average number of jobs in the system is ________.

  1. A) 100 percent; 10.625
  2. B) low; .0941
  3. C) 0.400 or 40 percent; 2.5
  4. D) 0.235 or 23.5 percent; 4.25
  5. E) maximized; minimized

Answer:  C

Diff: 2

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

18) Five welding jobs are waiting to be processed. Their processing times and due dates are given below. Using the critical ratio dispatching rule, in which order should the jobs be processed? All dates are specified as days from today.

 

Job

Processing Time (days)

Job due date (days)

A

4

7

B

2

4

C

8

11

D

3

5

E

5

11

 

  1. A) B, D, A, E, C
  2. B) C, D, A, B, E
  3. C) C, E, A, D, B
  4. D) E, B, A, D, C
  5. E) B, D, A, C, E

Answer:  B

Diff: 2

Key Term:  Critical ratio (CR)

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

19) Which critical ratio value implies that a job is already late?

  1. A) more than 100
  2. B) 1
  3. C) less than 1
  4. D) 10
  5. E) 3.4

Answer:  C

Diff: 2

Key Term:  Critical ratio (CR)

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

20) What is the priority rule that sequences jobs using the smallest ratio of due date from today to processing time?

  1. A) critical ratio
  2. B) earliest due date
  3. C) first come, first served
  4. D) longest processing time
  5. E) shortest processing time

Answer:  A

Diff: 2

Key Term:  Critical ratio (CR)

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

21) Which of the following is an advantage of the FCFS dispatching rule when used in services?

  1. A) FCFS maximizes utilization.
  2. B) FCFS minimizes the average number of jobs in the system.
  3. C) FCFS minimizes the average lateness of all jobs.
  4. D) FCFS maximizes the number of jobs completed on time.
  5. E) FCFS seems fair to customers.

Answer:  E

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

22) What does the use of the shortest processing time sequencing rule generally produce?

  1. A) maximum average lateness
  2. B) maximum utilization
  3. C) maximum effectiveness
  4. D) minimum average flow time
  5. E) B and D

Answer:  E

Diff: 2

Key Term:  Sequencing

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

23) When a set of jobs must pass through two workstations whose sequence is fixed, ________ is the sequencing rule most commonly applied.

  1. A) critical ratio
  2. B) earliest due date
  3. C) first come, first served
  4. D) slack time remaining
  5. E) Johnson's rule

Answer:  E

Diff: 2

Key Term:  Johnson's rule

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

24) Five jobs are waiting for processing through two work centers. Their processing time (in minutes) at each work center is contained in the table below. Each job requires work center Alpha before work center Beta. According to Johnson's rule, which job should be scheduled first in the sequence?

 

Job

Alpha

Beta

R

20

10

S

25

35

T

50

20

U

15

35

V

55

75

 

  1. A) R
  2. B) S
  3. C) T
  4. D) U
  5. E) V

Answer:  D

Diff: 2

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

25) Five jobs are waiting for processing through two work centers. Their processing time (in minutes) at each work center is contained in the table below. Each job requires work center Sigma before work center Delta. According to Johnson's rule, what sequence of jobs will minimize the completion time for all jobs?

Job

Sigma

Delta

R

40

10

S

25

30

T

50

20

U

35

35

V

55

15

 

  1. A) R-S-T-U-V
  2. B) S-V-T-R-U
  3. C) S-U-T-V-R
  4. D) V-R-U-S-T
  5. E) R-V-T-S-U

Answer:  C

Diff: 2

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

26) Which of the following is a limitation of rules-based dispatching systems?

  1. A) Rules need to be revised to adjust to changes in orders, product mix, and so forth.
  2. B) Rules may not recognize idle resources.
  3. C) Rules may not recognize bottleneck resources
  4. D) Rules may not be able to prioritize two jobs with identical due dates.
  5. E) All of the above are limitations.

Answer:  E

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

27) Five jobs are waiting for processing through two work centers. Their processing time (in minutes) at each work center is contained in the table below. Each job requires work center Alpha before work center Beta. According to Johnson's rule, what is the optimum sequence of jobs and the minimum time for completion of all jobs?

 

Job

Alpha

Beta

R

20

10

S

25

35

T

50

20

U

15

35

V

55

75

 

  1. A) V-T-S-U-R; 225
  2. B) U-R-T-S-V; 175
  3. C) R-S-T-U-V; 240
  4. D) U-S-V-T-R; 200
  5. E) R-U-T-S-V; 175

Answer:  D

Diff: 3

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

28) ________ determines the order in which jobs should be done at each work center.

Answer:  Sequencing

Diff: 1

Key Term:  Sequencing

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

29) ________ determine the sequence of jobs in process-oriented facilities.

Answer:  Priority rules

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

30) The priority rule that appears fair to customers in service systems is ________.

Answer:  first come, first served

Diff: 1

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

31) An approach to sequencing that can handle the situation where jobs must pass through two or more work centers in a fixed sequence is ________.

Answer:  Johnson's rule

Diff: 2

Key Term:  Johnson's rule

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

32) What does Johnson's rule do?

Answer:  Johnson's rule is an approach that minimizes the total time for sequencing a group of jobs through two work centers while minimizing total idle time in the work centers.

Diff: 2

Key Term:  Johnson's rule

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

33) In retail outlets, customers are usually processed on a first come, first served basis. Why? Is the express lane in the supermarket an exception? Craft a sequencing rule to explain express lane behavior.

Answer:  FCFS is fair. All customers are considered equally important, and no one should be given a higher priority than another. Most students will write a rule like, "Split by long vs. short processing times, then FCFS within each segment" or "FCFS, except for very short processing times." Note that "8 items or less" is a proxy for processing time.

Diff: 2

Key Term:  Priority rules

AACSB:  Reflective thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

34) What is the primary disadvantage of the shortest processing time dispatch rule? Is this a problem if there can be no new jobs arriving after the sequence is set?

Answer:  As new jobs arrive, new short-duration jobs will push back existing long-duration jobs in priority. If newly arriving jobs must wait for a new sequence to be built, this is less problematic.

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

35) Consider the arrival of patients into a public health clinic. Some patients are ill; some are injured; some are elderly; and some are very young. Some cases may be life-threatening, while others are inconsequential. How do the basic dispatch rules fall short in this situation? Design a dispatch rule for scheduling these patients.

Answer:  All of the rules are inappropriate, because they ignore the urgency of treating the most serious cases. There is also no "due date" on which to base lateness or critical ratio sequences. Most students will write a "priority" rule that behaves like triage–assigning an urgency code to each patient, and taking highest urgency cases first. Student rules may have more than one part; for example, patients may be sorted by urgency code, and by treatment time within urgency code. They may also create a separate code for contagious cases.

Diff: 2

Key Term:  Priority rules

AACSB:  Reflective thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

36) What are four main criteria by which we evaluate sequencing rules?

Answer:  There are a number of criteria for evaluating job sequencing rules. Criteria discussed in the text include average completion time, utilization metric, average number of jobs in the system, and average job lateness.

Diff: 2

Key Term:  Sequencing

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

37) What are some limitations of rule-based scheduling systems?

Answer:  Three limitations are (1) Rules need to be revised to adjust to changes in orders, process, equipment, product mix, etc.; (2) Rules do not look upstream or downstream; idle resources and bottleneck resources in other departments may not be recognized, and (3) Rules do not look beyond due dates.

Diff: 2

Key Term:  Priority rules

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

38) A practitioner of family medicine begins her day with five patients needing urgent care. She does a very brief assessment of what each patient appears to need and estimates the time required of each. None of the cases is life-threatening, and so she determines to take the five in the order that they arrived at the clinic. The processing-time data for these patients, in the order they arrived, are: Patient A, 30 minutes; Patient B, 40 minutes; Patient C, 10 minutes; Patient D, 50 minutes; and Patient E, 15 minutes.

(a)   If it is now 8:00 a.m., at what time will the doctor be finished with all five of these emergencies?

(b)   How much time will the five patients have collectively spent waiting?

(c)   How much less time would have been spent waiting if the doctor had taken the patients according to shortest processing time?

Answer: 

(a)  Using first come, first served, all five patients will be finished in 145 minutes, or at 10:25 a.m.

(b)  Total flow time is 455 minutes, of which 145 is for processing, and the remaining 310 is waiting time.

(c)   If the doctor had used shortest processing time, the total flow time would have been 330 minutes, of which 185 is waiting time. In both cases, the doctor finished all patients at 10:25 a.m. A supporting table for each rule appears below.

 

 

Processing Time

Due Date

 #Opns

Order

Flow time

A

30.

0.

0.

first

30.

B

40.

0.

0.

second

70.

C

10.

0.

0.

third

80.

D

50.

0.

0.

fourth

130.

E

15.

0.

0.

fifth

145.

Total

 

 

 

 

455.

Average

 

 

 

 

91.

Average # jobs in the system

3.1379

 

 

 

 

Sequence: A, B, C, D, E

 

 

Processing Time

Due Date

 #Opns

Order

Flow time

A

30.

0.

0.

third

55.

B

40.

0.

0.

fourth

95.

C

10.

0.

0.

first

10.

D

50.

0.

0.

fifth

145.

E

15.

0.

0.

second

25.

Total

 

 

 

 

330.

Average

 

 

 

 

66.

Average # jobs in the system

2.2759

 

 

 

 

Sequence; C, E, A, B, D

Diff: 2

Key Term:  Sequencing

AACSB:  Analytical thinking

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

39) Jack's Refrigeration Repair is under contract to repair, recondition, and/or refurbish commercial and industrial icemakers from restaurants, seafood processors, and similar organizations. Jack currently has five jobs to be scheduled, shown in the order in which they arrived.

 

Job

Processing Time (hours)

Due (hours)

V

20

50

W

10

35

X

50

90

Y

15

35

Z

55

75

 

(a)  Complete the following table. (Show your supporting calculations below).

(b)  Which dispatching rule has the best score for flow time?

(c)  Which dispatching rule has the best score for work-in-process (jobs in the system)?

(d)  Which dispatching rule has the best score for lateness?

 

Dispatching Rule

Job Sequence

Average Flow Time

Average Number of Jobs

Average Lateness

FCFS

 

 

 

 

SPT

 

 

 

 

EDD

 

 

 

 

CR

 

 

 

 

 

Answer: 

(a)  A summary of calculations appears in the table below.

 

Dispatching Rule

Job Sequence

Average Flow Time

Average Number of Jobs

Average Lateness

FCFS

V, W, X, Y, Z

75

2.50

27

SPT

W, Y, V, X, Z

65

2.17

16

EDD

W, Y, V, Z, X

66

2.20

17

CR

Z, X, Y, V, W

114

3.80

61

 

(b, c, d) SPT is best on all three criteria: flow time, work-in-process, and lateness. Supporting calculations for each priority rule appear in the tables below.

 

SPT

Machine1

Due Date

Flow Time

Late

W

10

35

10

0

Y

15

35

25

0

V

20

50

45

0

X

50

90

95

5

Z

55

75

150

75

Total

 

 

325

80

Average

 

 

65

16

Average # jobs in system = 2.17

 

 

FCFS

Machine1

Due Date

Flow Time

Late

V

20

50

20

0

W

10

35

30

0

X

50

90

80

0

Y

15

35

95

60

Z

55

75

150

75

Total

 

 

375

135

Average

 

 

75

27

Average # jobs in system = 2.5

 

EDD

Machine1

Due Date

Flow Time

Late

W

10

35

10

0

Y

15

35

25

0

V

20

50

45

0

Z

55

75

100

25

X

50

90

150

60

Total

 

 

330

85

Average

 

 

66

17

Average # jobs in system = 2.20

 

CR

Machine1

Due Date

CR

Flow Time

Late

Z

55

75

1.36

55

0

X

50

90

1.8

105

15

Y

15

35

2.33

120

85

V

20

50

2.5

140

90

W

10

35

3.5

150

115

Total

 

 

 

570

305

Average

 

 

 

114

6

 

Average # jobs in system = 3.80

Diff: 3

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

40) The operations manager of a body and paint shop has five cars to schedule for repair. He would like to minimize the throughput time (makespan) to complete all work on these cars. Each car requires body work prior to painting. The estimates of the times required to do the body and paint work on each are as follows:

 

Car

Body Work (Hours)

Paint (Hours)

A

8

7

B

9

4

C

7

9

D

3

4

E

12

5

 

(a)  Use Johnson's rule to sequence these five jobs for minimum total duration. Show your work in

determining the job sequence.

(b)  The optimal sequence is ________.

(c)   Chart the progress of the five jobs in this optimal sequence.

(d)  After how many hours will all jobs be completed?

Answer:  (a), (b) The sequence of jobs is Car D, Car C, Car A, Car E, Car B. See the POM for Windows solution below.

 

Johnson's method sequence of steps

 

(c), (d)

All jobs completed after 43 hours.

Diff: 3

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

41) The following jobs are waiting to be processed at your work center, which cleans valve body castings. Job numbers are assigned sequentially upon arrival in the facility (a missing number means that job does not require your work center). All dates are specified as days from today.

 

Job

Due Date

Duration (days)

101

43

10

102

34

12

104

37

11

107

32

7

108

37

15

 

  1. In what sequence should the jobs be processed according to the FCFS scheduling rule?
  2. In what sequence should the jobs be processed according to the EDD scheduling rule?
  3. In what sequence should the jobs be processed according to the SPT scheduling rule?
  4. In what sequence should the jobs be processed according to the LPT scheduling rule?
  5. In what sequence should the jobs be processed according to the critical ratio scheduling rule?

Answer: 

FCFS: 101, 102, 104, 107, 108

EDD: 107, 102, 104 and 108 (tie), 101

SPT: 107, 101, 104, 102, 108

LPT: 108, 102, 104, 101, 107

CR: 108 (2.47), 102 (2.83), 104 (3.36), 101 (4.30), 107 (4.57)

Diff: 2

Key Term:  Priority rules

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

42) At Morgan's Transformer Rebuilding, a set of five jobs is ready for dispatching to a machine center. The processing times and due dates for the jobs are given in the table below. Use shortest processing time to sequence the jobs, and calculate the average completion time, the average job lateness, and the average number of jobs in the machine center.

 

Job

Work Time (days)

Due Date (days)

A

15

38

B

13

28

C

7

20

D

18

50

E

9

15

 

Answer:  The optimal sequence is C-E-B-A-D. The average completion time is 31.6 days. The average lateness is 4 days. The average jobs in system is 2.548. Details appear in the table below.

 

SPT

Time

Due Date

Slack

Flow time

Late days

C

7

20

13

7

0

E

9

15

6

16

1

B

13

28

15

29

1

A

15

38

23

44

6

D

18

50

32

62

12

 

 

 

Total

158

20

 

 

 

Average

31.6

4

Average number of jobs in system: 2.548

Diff: 2

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

43) At Morgan's Transformer Rebuilding, five jobs are ready now for dispatching to a machine center. The processing times and due dates for the jobs are given below. Use earliest due date to sequence the jobs, and calculate the average completion time, the average job lateness, and the average number of jobs in the machine center.

 

Job

Work Time (days)

Due Date (days)

A

15

38

B

13

28

C

7

20

D

18

50

E

9

15

 

Answer:  The EDD sequence is E-C-B-A-D. Average completion time is 32 days. Average lateness is 3.8 days. Average number of jobs is 2.58

 

EDD

Time

Due Date

 

Slack

Flow time

Late days

E

9

15

 

6

9

0

C

7

20

 

13

16

0

B

13

28

 

15

29

1

A

15

38

 

23

44

6

D

18

50

 

32

62

12

 

 

 

 

Total

160

19

 

 

 

 

Average

32

3.8

Average number of jobs in system: 2.58

Diff: 2

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

44) Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on two machines in a fixed order (Machine 1 before Machine 2). The processing times are given in the table below.

  1. What is the optimal sequence?
  2. What is the total flow time for this sequence?

 

Job

Machine 1

Machine 2

L

10

11

M

8

17

N

14

9

O

13

7

P

10

8

 

Answer:  (a, b) The optimal sequence is M-L-N-P-O, and the total flow time is 62. Details are contained in the solution table below.

 

Diff: 2

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

45) A manufacturer has the following jobs waiting on a single work center. The firm has not decided which dispatching rule to apply in order to prioritize the jobs and fix them into the schedule. Processing time in 15-minute time blocks and due date for each job are in the table below.

 

 

Time

Due Date

Job 1

5

17

Job 2

4

20

Job 3

3

16

Job 4

7

9

Job 5

3

6

Job 6

5

7

 

  1. a) Complete the following table. Show your supporting calculations below.
  2. b) Which dispatching rule has the best score for flow time? for work in process (jobs in the system)? for lateness?
  3. c) Is there ANY sequence that can avoid all lateness? Explain or provide an example.

 

Dispatching Rule

 

Job Sequence

Average

Flow Time

Average Number of Jobs

 

Average Lateness

EDD

 

 

 

 

SPT

 

 

 

 

LPT

 

 

 

 

 

Answer: 

(a) The results appear in the table below. A supporting table for each dispatch rule also follows.

 

Dispatching Rule

 

Job Sequence

Average

Flow Time

Average Number of Jobs

Average Lateness

EDD

5-6-4-3-1-2

15.67

3.48

3.67

SPT

3-5-2-1-6-4

13.50

3.00

5.17

LPT

4-6-1-2-5-3

18.00

4.00

5.83

 

(b, c, d) SPT is best for flow time, and for average jobs in system; EDD is best for lateness.

(e) Lateness is unavoidable with any dispatch rule; the sum of processing times is 27 but the longest due date is only 20 days away.

 

 

EDD

Time

Due Date

Slack

Flow time

Late days

Job 5

3

6

3

3

0

Job 6

5

7

2

8

1

Job 4

7

9

2

15

6

Job 3

3

16

13

18

2

Job 1

5

17

12

23

6

Job 2

4

20

16

27

7

 

 

 

Total

94

22

 

 

 

Average

15.67

3.667

Average number of jobs in system: 3.481

 

SPT

Time

Due Date

Slack

Flow time

Late days

Job 3

3

16

13

3

0

Job 5

3

6

3

6

0

Job 2

4

20

16

10

0

Job 1

5

17

12

15

0

Job 6

5

7

2

20

13

Job 4

7

9

2

27

18

 

 

 

Total

81

31

 

 

 

Average

13.5

5.167

Average number of jobs in system: 3

 

LPT

Time

Due Date

Slack

Flow time

Late days

Job 4

7

9

2

7

0

Job 6

5

7

2

12

5

Job 1

5

17

12

17

0

Job 2

4

20

16

21

1

Job 5

3

6

3

24

18

Job 3

3

16

13

27

11

 

 

 

Total

108

35

 

 

 

Average

18

5.83

Average number of jobs in system: 4

 

Diff: 3

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

46) Bob Dresser operates a major appliance warranty service center. His operation has two check stations that are required at the end of every repair task performed by his appliance repair staff. These are the Functionality Review (FR) and the Overall Scan (OS). The FR must be performed successfully before the OS is begun. On Friday morning, six repair jobs are completed, awaiting these two inspection activities. Processing times are given in minutes.

 

Job

FR

OS

A

50

30

B

35

55

C

25

20

D

20

35

E

15

10

F

10

25

 

  1. What is the optimal sequence of jobs for the objective of minimizing the total flow time?
  2. Show your work, and document the sequence.
  3. Chart the solution to this problem.
  4. What jobs are being processed at time period 90?
  5. What is the total flow time of this problem?

 

FR

 

 

 

 

 

 

 

 

 

 

OS

 

 

 

 

 

 

 

 

 

 

 

20

40

60

80

100

120

140

160

180

200

 

Answer: 

(a)  The optimal sequence is F-D-B-A-C-E.

(b)  Supporting work appears in the table below.

 

 

(c)   The schedule appears in the chart below. (d) Job A is being processed at FR (Machine 1), while Job B is being processed at OS (e) Total flow time for the schedule is 185.

 

(Machine 2)

Diff: 3

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

47) A firm that specializes in desktop publishing for local charities has agreed to take on the following jobs. The firm has not decided which dispatching rule to apply in order to prioritize the jobs and fix them into the schedule. All dates are specified as days from today.

 

 

Time

Due Date

Job 1

20

25

Job 2

15

20

Job 3

7

16

Job 4

25

50

Job 5

31

33

Job 6

43

55

 

  1. Complete the following table. Show your supporting calculations below.
  2. Which dispatching rule has the best score for flow time?
  3. Which dispatching rule has the best score for work-in-process (jobs in the system)?
  4. Which dispatching rule has the best score for lateness?

 

Dispatching Rule

 

Job Sequence

Average

Flow Time

Average Number of Jobs

 

Average Lateness

FCFS

 

 

 

 

EDD

 

 

 

 

SPT

 

 

 

 

LPT

 

 

 

 

 

Answer: 

(a)  The table of results appears below. A supporting table for each dispatch rule also follows.

 

Dispatching Rule

 

Job sequence

Average

Flow Time

Average Number of Jobs

Average Lateness

FCFS

1-2-3-4-5-6

67.2

2.86

34.8

EDD

3-2-1-5-4-6

63.8

2.71

32.2

SPT

3-2-1-4-5-6

62.8

2.67

31.2

LPT

6-5-4-1-2-3

101.7

4.33

70.5

 

(b, c, d) The SPT rule is best for flow time, for average jobs in system, and for average lateness.

 

FCFS

Time

Due Date

 

Slack

Flow time

Late days

Job 1

20

25

 

5

20

0

Job 2

15

20

 

5

35

15

Job 3

7

16

 

9

42

26

Job 4

25

50

 

25

67

17

Job 5

31

33

 

2

98

65

Job 6

43

55

 

12

141

86

 

 

 

 

Total

403

209

 

 

 

 

Average

67.17

34.83

Average number of jobs in system: 2.858

 

EDD

Time

Due Date

 

Slack

Flow time

Late days

Job 3

7

16

 

9

7

0

Job 2

15

20

 

5

22

2

Job 1

20

25

 

5

42

17

Job 5

31

33

 

2

73

40

Job 4

25

50

 

25

98

48

Job 6

43

55

 

12

141

86

 

 

 

 

Total

383

193

 

 

 

 

Average

63.83

32.17

Average number of jobs in system: 2.716

 

SPT

Time

Due Date

 

Slack

Flow time

Late days

Job 3

7

16

 

9

7

0

Job 2

15

20

 

5

22

2

Job 1

20

25

 

5

42

17

Job 4

25

50

 

25

67

17

Job 5

31

33

 

2

98

65

Job 6

43

55

 

12

141

86

 

 

 

 

Total

377

187

 

 

 

 

Average

62.83

31.17

Average number of jobs in system: 2.674

 

LPT

Time

Due Date

 

Slack

Flow time

Late days

Job 6

43

55

 

12

43

0

Job 5

31

33

 

2

74

41

Job 4

25

50

 

25

99

49

Job 1

20

25

 

5

119

94

Job 2

15

20

 

5

134

114

Job 3

7

16

 

9

141

125

 

 

 

 

Total

610

423

 

 

 

 

Average

101.67

70.5

Average number of jobs in system: 4.326

Diff: 3

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

48) Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on two machines in a fixed order (Machine 1 before Machine 2). The processing times in hours are given in the table below.

  1. What is the optimal sequence?
  2. What is the total flow time for this sequence?

 

Job

Machine 1

Machine 2

A

10

11

B

8

17

C

14

10

D

13

7

E

10

8

F

25

9

G

6

15

 

Answer:  (a, b) The optimal sequence is G-B-A-C-F-E-D, and the total flow time is 93 hours, as shown in the software solution below.

 

Diff: 3

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

49) There are 5 jobs (A, B, C, D, E) that need to be completed in a work center. The due dates are the 10th, 13th, 9th, 20th, and 15th respectively with process times of 7, 12, 7, 20, and 10 respectively as well. If today is the 1st of the month calculate the critical ratio for each and use this value to sequence the jobs in the order they should be started.

Answer:  A = (10 - 1)/7 = 1.29

B = (13 - 1)/12 = 1.00

C = (9 - 1)/7 = 1.14

D = (20 - 1)/20 = 0.95

E = (15 - 1)/10 = 1.40

Thus the sequence would be DBCAE, or lowest critical ratio first

Diff: 2

Key Term:  Critical ratio (CR)

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

50) Given the table below, find the sequence for the following priority rules:

(a)  SPT

(b)  EDD

(c)  LPT

 

Job

Process Time

Due Date

A

6

10

B

4

2

C

8

5

D

9

16

 

Answer: 

(a)  BACD

(b)  BCAD

(c)  DCAB

Diff: 1

Key Term:  Priority rules

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

51) Given the following chart of jobs assigned with Johnson's rule, suppose that all the jobs (A, B, C, etc) could be evenly divided into two tasks (such as A1 and A2, B1 and B2, etc). Suppose job B is divided into jobs B1 and B2, each with a body work time of 4.5 hours and a paint time of 2 hours. How much is makespan reduced by this splitting of B?

 

 

Answer:  B1 could start on paint at time = 34.5 (1/2 through the completion of B) but E is busy on paint until t = 35, thus B1 will be delayed until t = 35 to start and thus would finish paint at time = 37. B2 could start on paint at time = 39 and would take until t = 41 to finish. Thus makespan is reduced by 2 hours (43 - 41).

Diff: 2

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

52) Given the following chart of jobs assigned with Johnson's rule, suppose that all the jobs (A, B, C, etc) could be evenly divided into two tasks (such as A1 and A2, B1 and B2, etc). Suppose job D is split into two equivalently sized sections, D1 and D2, each with a body work time of 1.5 hours and a paint time of 2 hours (D1 and D2 sum to 3 hours of body work and 4 hours of paint which is equivalent to D). How much is makespan reduced by this splitting of D?

 

 

Answer:  Job D1 could now start paint at t = 1.5 and would finish at t = 3.5 Job D2 could start paint at t = 3, however paint is occupied until t = 3.5. Thus D2 will start paint at t = 3.5 and finish at t = 5.5. However, this does nothing to save makespan time because C will not start on paint until t = 10.

Diff: 2

Key Term:  Johnson's rule

AACSB:  Analytical thinking

Objective:  LO 15.5 Use Johnson's rule

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

53) Complete the table; find average lateness, average completion time, and average number of jobs in the system. Assume all durations are in days and that the jobs are processed at the shop in the order that they arrive (A then B then C then D).

 

Job

Process Time

Flow Time

Due Date

Lateness

A

5

 

7

 

B

3

 

9

 

C

2

 

12

 

D

5

 

4

 

Sum (Average)

15 (3.75)

 

XXXXX

 

 

Answer: 

Job

Process Time

Flow Time

Due Date

Lateness

A

5

5

7

0

B

3

8

9

0

C

2

10

12

0

D

5

15

4

11

Sum (Average)

         15 (3.75)

         38 (9.5)

XXXXX

          11 (2.75)

 

Avg lateness = 11/4 = 2.75 days

Avg completion time = 38/4 = 9.5 days

Avg number of jobs in the system = 38/15 = 2.53 jobs

Diff: 2

Key Term:  Sequencing

AACSB:  Analytical thinking

Objective:  LO 15.4 Name and describe each of the priority sequencing rules

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

Section 6   Finite Capacity Scheduling (FCS)

 

1) Finite capacity scheduling provides the user with graphical interactive computing, which is the technique's primary advantage over rule-based scheduling.

Answer:  TRUE

Diff: 2

Key Term:  Finite capacity scheduling (FCS)

AACSB:  Information technology

Objective:  LO 15.6 Define finite capacity scheduling

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

 

2) A recent advance in short-term scheduling that makes use of expert systems and simulation in solving dynamic scheduling problems is:

  1. A) forward scheduling.
  2. B) backward scheduling.
  3. C) infinite scheduling.
  4. D) finite capacity scheduling.
  5. E) progressive scheduling.

Answer:  D

Diff: 2

Key Term:  Finite capacity scheduling (FCS)

AACSB:  Information technology

Objective:  LO 15.6 Define finite capacity scheduling

Learning Outcome:  Describe the stages of short-term and long-term scheduling

3) ________ uses computerized short-term scheduling to overcome the disadvantages of rule-based systems by providing the user with interactive computing and graphical output.

Answer:  Finite capacity scheduling

Diff: 2

Key Term:  Finite capacity scheduling (FCS)

AACSB:  Information technology

Objective:  LO 15.6 Define finite capacity scheduling

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

4) What is finite capacity scheduling (FCS)?

Answer:  FCS is computerized short-term scheduling that overcomes the disadvantages of rule-based systems by providing the user with graphical interactive computing.

Diff: 2

Key Term:  Finite capacity scheduling (FCS)

AACSB:  Information technology

Objective:  LO 15.6 Define finite capacity scheduling

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

Section 7   Scheduling Services

 

1) Scheduling optimization systems used in retail stores typically track customer traffic in 4-hour time increments.

Answer:  FALSE

Diff: 3

AACSB:  Information technology

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

2) In services, the scheduling emphasis is usually on staffing levels, not materials.

Answer:  TRUE

Diff: 1

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

3) Because of the significance of labor in the scheduling of services, behavioral and social issues, wage and hour laws, and union contracts all complicate the scheduling process.

Answer:  TRUE

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

4) In manufacturing scheduling, physical inventories of goods can buffer variations in demand, but service scheduling normally lacks that buffer because services are generally consumed at the same time they are delivered.

Answer:  TRUE

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

5) Which of the following is NOT tracked by scheduling optimization systems used in retail stores?

  1. A) cars parked in the parking lot
  2. B) individual store sales
  3. C) transactions
  4. D) units sold
  5. E) customer traffic

Answer:  A

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

6) Which of the following is TRUE regarding services scheduling?

  1. A) The critical ratio sequencing rule is widely used for fairness to customers.
  2. B) The emphasis is on staffing levels, not materials.
  3. C) Reservations and appointments are often used to manipulate the supply of services.
  4. D) Labor use can be intensive, and labor demand is usually stable.
  5. E) All of the above are true.

Answer:  B

Diff: 2

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

7) In what five ways does the problem of scheduling service systems differ from that of scheduling manufacturing systems?

Answer: 

  1. In manufacturing, emphasis is on machines and materials, whereas in services it is on staffing levels.
  2. Inventories can help smooth demand for manufacturers, but many service systems do not maintain inventories.
  3. Services are labor intensive, and demand for this labor can be highly variable.
  4. Legal considerations, such as wage and hour laws and union contracts that limit hours worked per shift, week, or month, constrain scheduling decisions.
  5. Behavioral, social, seniority, and status issues complicate service scheduling.

Diff: 3

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

8) Identify some scheduling optimization systems that are used at retail stores. Describe what these systems do.

Answer:  Workbrain, Cybershift, and Kronos. These systems track individual store sales, transactions, units sold, and customer traffic in 15-minute increments to create work schedules.

Diff: 3

AACSB:  Information technology

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

9) The emergency room at a hospital estimates the following requirements for registered nurses (RNs) for the late night shift each week. Nurses work four consecutive days, then have off three days.

 

Sunday

Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

3

4

2

2

3

6

4

 

Perform cyclical scheduling on the data. (Note that you must identify three-day patterns of minimum requirements). How many RNs are required? How much extra capacity is required?

Answer: 

 

Days off are shaded. Seven full-time RNs are needed; an eighth works Friday only. A total of 29 shifts are used, while only 24 are required; thus 5 shifts represent excess capacity. This solution is not unique, as there are two instances where an arbitrary set of days was selected for minimum sum.

Diff: 3

AACSB:  Analytical thinking

Objective:  LO 15.7 Use the cyclical scheduling technique

Learning Outcome:  Describe the stages of short-term and long-term scheduling

 

----------------------------------

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