Operations Management: Processes and Supply Chains, 12e (Krajewski)
Supplement J Operations Scheduling
1) Operations scheduling involves assigning jobs to workstations or employees to jobs for specific time
periods.
2) Operations scheduling applies only to manufacturing, because services do not allow inventories.
3) Makespan is the time of completion of a group of jobs, plus the starting time of the first job.
4) Makespan is the total amount of time to complete a single job or the first job in a group of jobs.
5) In the context of operations scheduling, total inventory is the sum of the scheduled receipts for all
items and the on-hand inventories for all items.
6) An appropriate objective for a manufacturing firm is to maximize total inventory.
7) Utilization is the degree to which equipment, space, or the workforce is currently being used,
measured as the ratio of average output rate to the maximum capacity.
8) Which of the following statements on an operations schedule is best?
A) It determines when employees work.
B) It assigns employees to tasks depending on availability.
C) It assigns customers to a definite time for order fulfillment.
D) It assigns jobs to workstations or employees to jobs for specified time periods.
9) A job’s flow time at a single workstation is defined as the:
A) completion time of the job plus the time since it arrived at the workstation.
B) processing time to complete the job.
C) time of completion of the last job of a group minus the starting time of the first job.
D) amount of time by which a group of jobs missed their due dates.
10) In the context of operations scheduling, total inventory is equal to:
A) scheduled receipts plus on-hand inventories.
B) received orders minus scheduled receipts.
C) on-hand inventories plus received orders.
D) None of these is equal to total inventory.
11) The percent of work time productively spent by an employee or a machine is called:
A) activation.
B) efficiency.
C) effectiveness.
D) utilization.
12) ________ scheduling assigns jobs to machines or employees to jobs.
13) ________ is the time a job spends in the service or manufacturing system.
14) A(n) ________ is the object receiving service or being manufactured.
15) ________ is the total amount of time required to complete a group of jobs.
16) ________ is the amount of time by which a job missed its due date.
17) The sum of scheduled receipts for all items and the on-hand inventories for all items is ________.
18) ________ is the degree to which equipment, space, or the workforce is currently being used.
19) Why is flow time an important measure of performance?
20) Describe the difference between front office and back office operations from the standpoint of
scheduling customer jobs.
Answer: Front office operations are customer-facing (high customer contact) and typically have highly
divergent work flows and a high degree of customization. The demands on front-office operations are
J.2 Job Shop Scheduling
1) Sequencing jobs does not affect tardiness, because processing times are unchanged with different
sequences.
2) The fact that job shops routinely accept new orders at any time makes the scheduling environment
dynamic.
3) A job shop is accompanied by divergent flows and low–to-medium volume output rates.
4) A manufacturer‘s flow shop utilizes line or continuous flow processes.
5) The earliest due date (EDD) rule gives the job with the shortest processing time the highest priority.
6) A first-come, first-served schedule minimizes the average flow time for all jobs.
7) Critical ratio (CR) is a single-dimension priority rule.
8) Slack is the difference between the time remaining until a job’s due date and the total shop time
remaining, excluding that of the operation being scheduled.
9) When using the critical ratio (CR) priority sequencing rule:
A) a ratio of less than 1.0 implies that the job is ahead of schedule.
B) a ratio of less than 1.0 implies the job is behind schedule.
C) the job with the earliest due date is scheduled next.
D) the job with the highest CR is scheduled next.
10) Which one of the following rules tends to perform well with respect to percentage of jobs past due
and variance of hours past due, but performs relatively poorly with respect to average flow time?
A) earliest due date
B) shortest processing time
C) first-come, first-served
D) longest processing time
11) When choosing a priority sequencing rule:
A) select multiple-dimension rules because they dominate single-dimension rules for all performance
measures.
B) always select the rule that minimizes the amount of past–due jobs.
C) test a variety of rules before making a decision.
D) select CR or S/RO because they use more information.
12) Determining a production sequence for a group of jobs in a two-station flow shop to minimize the
makespan has the advantage of:
A) maximizing the utilization of the shop.
B) minimizing the percentage of jobs past due.
C) minimizing the flow time of jobs on the first machine.
D) minimizing the variance of past-due hours.
Table J.1
The framing department has six jobs waiting to be processed. It is now time zero. Times are expressed in
terms of days.
Job
Time Since
Job
Arrived
Processing
Time
Due
Date
A
8
5
12
B
7
7
18
C
6
8
6
D
4
3
10
E
2
9
22
F
1
12
17
13) Using the information in Table J.1 and the SPT rule, what is the average flow time?
A) fewer than or equal to 19 days
B) greater than 19 days but fewer than or equal to 21 days
C) greater than 21 days but fewer than or equal to 23 days
D) greater than 23 days
14) Using the information in Table J.1 and the EDD rule, what is the average flow time?
A) fewer than or equal to 25 days
B) greater than 25 days but fewer than or equal to 27 days
C) greater than 27 days but fewer than or equal to 29 days
D) greater than 29 days
15) Using the information in Table J.1 and the EDD rule, what is the average early time?
A) 0 days
B) greater than 0 but less than 1.5 days
C) greater than 2.5 but less than 2.5 days
D) greater than 2.5 days
16) Using the information in Table J.1 and the SPT rule, what is the average past due?
A) 0 days
B) greater than 0 days but fewer than or equal to 5 days
C) greater than 5 days but fewer than or equal to 10 days
D) greater than 10 days
17) Using the information in Table J.1 and the FCFS rule, what is the average flow time?
A) fewer than or equal to 19 days
B) greater than 19 days but fewer than or equal to 21 days
C) greater than 21 days but fewer than or equal to 23 days
D) greater than 23 days
18) Using the information in Table J.1 and the FCFS rule, what is the average past due?
A) 0 days
B) greater than 0 days but fewer than or equal to 5.5 days
C) greater than 5.5 days but fewer than or equal to 10 days
D) greater than 10 days
Table J.2
Stu Dent reviews the syllabi he received on the first day of class and pulls out his planner. He has seven
major assignments that must be completed before the end of the semester.
Job
Time Since
Job
Arrived
Processing
Time
Due Date
A
0
7
14
B
0
12
22
C
0
5
12
D
0
11
56
E
0
9
26
F
0
8
42
G
0
15
59
19) What is the average flow time for all assignments scheduled in an SPT sequence?
A) 28.65
B) 32.14
C) 35.92
D) 36.88
20) Develop an SPT sequence and calculate the average number of assignments Stu has this semester.
A) 3.36
B) 3.52
C) 3.78
D) 3.94
21) Stu decides to adopt an SPT sequence for the assignments, which at face value seems like an odd
choice. Which assignments will he be submitting late?
A) C, D and F
B) B, C and F
C) B, E and G
D) F, E and G
22) Stu decides to adopt an EDD sequence for the assignments, which seems like a very logical approach.
Which assignments will he be submitting late?
A) C, D and F
B) B, C and F
C) B, E and G
D) F, E and G
23) Stu applies the critical ratio method to scheduling his assignments. Which assignment is the fourth
one in his sequence?
A) E
B) G
C) C
D) D
24) What is the average flow time for all seven assignments if Stu schedules them using the critical ration
criterion?
A) 38.17
B) 37.43
C) 36.67
D) 38.26
25) Stu schedules his assignments using the critical ratio criterion. How many assignments are late?
A) 3
B) 4
C) 5
D) 6
26) Stu whips up a schedule based on the critical ratio criterion. What is the average number of
assignments in the system?
A) 3.91
B) 3.71
C) 3.53
D) 3.14
Table J.5
The following three jobs just arrived (end of hour 0) at Workstation A. They are the only ones waiting to
be processed.
Job
Processing Time
at Workstation A
(hours)
Time Remaining
to Due Date
(days)
Number of
Remaining
Operations
1
12
3
2
2
18
10
5
3
7
7
2
27) Use the information in Table J.5. The sequence of jobs using the slack per remaining operations (S/RO)
rule, is:
A) 1-3-2
B) 3-2-1
C) 1-2-3
D) 2-3-1
28) Use the information in Table J.5. The operations sequence of jobs, using the critical ratio (CR) rule, is
A) 3-1-2
B) 3-2-1
C) 1-2-3
D) 2-3-1
29) Use the information in Table J.5. The average past due using the slack per remaining operations
(S/RO) rule is:
A) fewer than or equal to 9.0.
B) greater than 9.0 but fewer than or equal to 18.0.
C) greater than 18.0 but fewer than or equal to 27.0.
D) greater than 27.0.
30) Use the information in Table J.5. The average past due using the ratio (CR) rule, is:
A) fewer than or equal to 9.0.
B) greater than 9.0 but fewer than or equal to 18.0.
C) greater than 18.0 but fewer than or equal to 27.0.
D) greater than 27.0.
Table J.6
All of the following three jobs just arrived (end of hour 0) at Workstation A. They are the only ones
waiting to be processed.
Job
Processing Time at
Workstation A (hours)
Time Remaining to
Due Date (days)
Shop Time Remaining
Including Workstation
A (days)
1
6.1
5
3.5
2
5.0
3
4.7
3
4.3
8
10.3
31) Use the information in Table J.6. What is the job sequence at Workstation A, using the critical ratio
rule?
A) 3-2-1
B) 1-2-3
C) 1-3-2
D) 2-1-3
32) Use the information in Table J.6. What is the average flow time at Workstation A for the critical ratio
rule?
A) fewer than or equal to 8 hours
B) greater than 8 hours but fewer than or equal to 9 hours
C) greater than 9 hours but fewer than or equal to 10 hours
D) greater than 10 hours
33) Use the information in Table J.6. What is the average past due time at Workstation A for the critical
ratio rule?
A) 0 hours
B) greater than 0 hours but fewer than or equal to 5 hours
C) greater than 5 hours but fewer than or equal to 10 hours
D) greater than 10 hours
Table J.7
The following four jobs just arrived (end of hour 0) at Workstation A. They are the only ones waiting to
be processed.
Job
Processing Time
at Workstation A
(hours)
Time Remaining
to Due Date
(days)
Number of
Remaining
Operations
1
4.0
5
2
2
5.0
4
1
3
6.0
8
3
4
7.0
9
1
34) Using the information in Table J.7 and the slack per remaining operations (S/RO) rule, what is the job
sequence?
A) A-B-C-D
B) A-C-D-B
C) C-D-B-A
D) D-C-B-A
35) Using the information in Table J.7 and the S/RO rule, what is the average flow time at Workstation A?
A) fewer than or equal to 14.0 hours
B) greater than 14.0 but fewer than or equal to 14.5 hours
C) greater than 14.5 but fewer than or equal to 15.0 hours
D) greater than 15.0 hours
36) Using the information in Table J.7 and the critical ratio (CR) rule, what is the job sequence?
A) C-D-B-A
B) D-C-B-A
C) A-C-D-B
D) D-B-A-C
37) Using the information in Table J.7 and the CR rule, what is the average flow time at workstation A?
A) fewer than or equal to 14.0 hours
B) greater than 14.0 but fewer than or equal to 14.5 hours
C) greater than 14.5 but fewer than or equal to 15.0 hours
D) greater than 15.0 hours
Table J.8
Auto Data produces custom engineering testing equipment. The following six jobs are currently in the
design department. The time since each one arrived, the processing time, and the due date are shown
below. All times are expressed in terms of days. Let now be the beginning of Day 1.
Job
Time Since Job
Arrived
Processing
Time
Due Date
A
2
8
15
B
8
6
11
C
2
7
22
D
11
5
8
E
9
3
9
F
4
9
16
38) Using the information in Table J.8 and the EDD rule, what is the average days past due?
A) fewer than or equal to 8.0 days
B) greater than 8.0 days but fewer than or equal to 9.5 days
C) greater than 9.5 but fewer than or equal to 11.0 days
D) greater than 11.0 days
39) Using the information in Table J.8 and the SPT rule, what is the average days past due?
A) fewer than or equal to 6.0 days
B) greater than 6.0 days but fewer than or equal to 7.0 days
C) greater than 7.0 days but fewer than or equal to 8.0 days
D) greater than 8.0 days
40) Using the information in Table J.8 and the FCFS rule, what is the average days past due?
A) fewer than or equal to 5.0 days
B) greater than 5.0 days but fewer than or equal to 8.0 days
C) greater than 8.0 days but fewer than or equal to 9.0 days
D) greater than 9.0 days
41) Using the information in Table J.8, and either the FCFS, SPT or EDD rule, what is the fewest number
of late jobs possible?
A) no late jobs
B) one late job
C) two late jobs
D) three late jobs
Table J.9
There are three jobs available for processing at Workstation 1. They just arrived at Workstation 1, at the
end of Day 0.
Job
Processing
Time at
Workstation 1
(hours)
Time
Remaining to
Due Date
(days)
Shop Time
Remaining
Including
Workstation 1
(days)
Remaining
Number of
Operations
A
4.0
5
4
2
B
5.0
4
4
1
C
6.0
8
10
3
42) Using the information in Table J.9 and the slack per remaining operations (S/RO) rule, what should be
the sequence of jobs processed at Workstation 1?
A) A-B-C
B) B-C-A
C) C-B-A
D) B-A-C
43) Using the information in Table J.9 and the critical ratio rule, what should be the sequence of jobs
processed at Workstation 1?
A) C-B-A
B) B-A-C
C) A-B-C
D) B-C-A