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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.
2) Short-term scheduling is important to efficiency and to cost reduction, but its impact is not of strategic
importance.
3) The benefits of effective scheduling include lower cost, faster throughput, and dependable delivery.
4) Which of the following statements regarding scheduling at Alaska Airlines is FALSE?
A) Flying into Alaska complicates scheduling.
B) Schedule changes at one airport have a ripple effect that may have impacts in many others.
C) Alaska Airlines' high-tech computer and communications system is located in Seattle.
D) Alaska Airlines' rapid rescheduling uses mathematical scheduling models.
E) Alaska Airlines' rapid rescheduling promotes air safety and limits traveler inconvenience, but has not
resulted in money savings for Alaska Airlines.
5) Which of the following is NOT a key direct benefit from effective internal or external scheduling?
A) lower cost
B) greater use of assets
C) more dependable delivery
D) higher quality
E) added flexibility
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.
7) What makes short-term scheduling of strategic importance?
Section 2 Scheduling Issues
1) With forward scheduling, jobs are scheduled as late as possible within the time allowed by the
customer due dates.
2) One criterion for developing effective schedules is minimizing completion time.
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.
4) What is the objective of scheduling?
A) maximize quality
B) minimize cost
C) minimize response time
D) prioritize and allocate demand to available facilities
E) minimize lead time
5) The correct sequence from longest to smallest duration scheduling is:
A) capacity planning, aggregate planning, master schedule, short-term scheduling.
B) aggregate planning, capacity planning, master schedule, short-term scheduling.
C) master schedule, capacity planning, aggregate planning, short-term scheduling.
D) master schedule, aggregate planning, capacity planning, short-term scheduling.
E) capacity planning, master schedule, aggregate planning, short-term scheduling.
6) Forward scheduling is the scheduling of:
A) the end items or finished products.
B) jobs as soon as the requirements are known.
C) the start items or component parts.
D) the final operation first beginning with the due date.
E) jobs according to their profit contributions.
7) Short-term schedules are prepared:
A) directly from the aggregate plans.
B) directly from the capacity plans.
C) from inventory records for items that have been used up.
D) from master schedules, which are derived from aggregate plans.
E) from the purchasing plans.
8) Which of the following is not an effectiveness criterion for scheduling?
A) minimizing customer waiting time
B) minimizing completion time
C) minimizing WIP inventory
D) maximizing utilization
E) maximizing flow time
9) Which of the following considers process capacity when scheduling?
A) cap loading
B) constrained loading
C) capacitated loading
D) backward loading
E) finite loading
10) Forward scheduling:
A) begins with a delivery date, then offsets each operation one at a time, in reverse order.
B) has the same meaning as "finite loading."
C) is often used in service environments such as catering a banquet or scheduling surgery.
D) starts the schedule as soon as the job requirements are known.
E) produces a schedule only if it meets the due date.
11) The short-term scheduling activity called "loading":
A) assigns dates to specific jobs or operations steps.
B) specifies the order in which jobs should be done at each center.
C) assigns jobs to work centers
D) assigns workers to jobs.
E) assigns workers to machines.
12) ________ scheduling begins with the due date and schedules the final operation first and the other job
steps in reverse order.
13) In the sequence of decisions that affect scheduling, ________ is (are) the immediate follower(s) of the
master schedule (or master production schedule).
14) ________ is the assignment of jobs to work or processing centers.
15) Explain, in your own words, how backward scheduling and forward scheduling differ.
16) Compare short-term scheduling at process-focused, repetitive, and product-focused facilities.
Section 3 Scheduling Process-Focused Facilities
1) Which of the following is NOT required to be known in order to schedule process-focused facilities?
A) the sequence of work
B) which workers are assigned to each work center
C) the time required for each item
D) the capacity of each work center
E) the availability of each work center
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.
2) A Gantt load chart shows the loading and idle time of several departments, machines, or facilities.
3) Gantt charts are useful for scheduling jobs, but not for loading them.
4) The assignment method provides an optimum, one-to-one assignment of jobs to resources.
5) A work center had actual input of 280 hours and actual output of 270 hours. What is the change in
backlog?
A) 10
B) -10
C) 0
D) 1.037
E) Unable to determine with the given information
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?
A) 0
B) 1
C) -1
D) 58
E) Unable to determine with the given information
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:
A) MRP.
B) ConWIP cards.
C) Gantt charts.
D) Johnson's rule.
E) the assignment method.
8) The assignment method is:
A) a method to highlight overloads in a given work center.
B) a computerized method of determining appropriate tasks for an operation.
C) a form of linear programming for optimally assigning tasks or jobs to resources.
D) the same thing as the Gantt schedule chart.
E) a method for achieving a balance between forward and backward scheduling.
9) What is a scheduling technique used to achieve an optimum, one-to-one matching of tasks and
resources?
A) the assignment method
B) Johnson's rule
C) the CDS algorithm
D) the appointment method
E) the reservation method
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?
A) worker A assigned to job 1 and worker B assigned to job 2
B) worker A assigned to job 2 and worker B assigned to job 1
C) worker A gets both jobs 1 and 2
D) worker B gets both jobs 1 and 2
E) unable to determine
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?
A) 3, 4, 5
B) 8, 9, 10
C) 0, 1, 2
D) 6, 7, 8
E) 1, 4/3, 5/3
12) Which of the following is an aid used to monitor jobs in progress?
A) a Gantt load chart
B) the assignment method
C) a Gantt schedule chart
D) Johnson's rule
E) a Gantt progress chart
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?
A) the assignment method
B) backward scheduling
C) forward scheduling
D) ConWIP cards
E) level material use
14) If an assignment problem consists of 6 workers and 7 projects:
A) one worker will not get a project assignment.
B) one worker will be assigned two projects.
C) each worker will contribute work toward the seventh project.
D) one project will not get a worker assigned.
E) The problem cannot be solved by assignment method.
15) If an assignment problem consists of 5 workers and 4 projects:
A) one worker will not get a project assignment.
B) one project will be assigned two workers.
C) the fifth worker will split time among the four projects.
D) one project will not get a worker assigned.
E) The problem cannot be solved by assignment method.
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
A) the row for Job 1 contains the values 5, 6, and 0.
B) calculations are complete, and the problem is ready for an optimal set of assignments.
C) the column for Machine B indicates that it should be retired.
D) Job 1 should be performed on Machine B.
E) Job 1 should be performed on Machine A.
17) ________ cards are used to control the amount of work in a work center, aiding input-output control.
18) ________ are planning charts used to schedule resources and allocate time.
19) The ________ is a special class of linear programming models that involves assigning tasks or jobs to
resources.
20) What is input-output control?
21) What is the assignment method?
22) Identify the major disadvantages of the Gantt load chart.
23) What is the difference between a Gantt load chart and a Gantt scheduling chart?
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?
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
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
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.
2) The critical ratio sequencing rule prioritizes the jobs based on the importance or value of the customers
who have placed the orders.
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.
4) Johnson's rule sequences a set of jobs through two different machines or work centers in the same
order.
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
A) 0.0 days
B) 24.0 days
C) 7.4 days
D) 9.0 days
E) 11.6 days
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
A) 47.6 days
B) 60.2 days
C) 94.0 days
D) 2.5 days
E) 238.0 days
7) EDD stands for what?
A) earliest due date
B) earliest design date
C) earliest detrimental date
D) earliest decision date
E) economic date determination
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?
A) ABCD
B) DCBA
C) DACB
D) DABC
E) BCAD
9) Orders are processed in the sequence in which they arrive if (the) ________ rule sequences the jobs.
A) earliest due date
B) slack time remaining
C) first come, first served
D) critical ratio
E) Johnson's
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?
A) shortest processing time (SPT)
B) critical ratio (CR)
C) first in, first out (FIFO)
D) first come, first served (FCFS)
E) longest processing time (LPT)
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
A) A, B, C, D, E
B) C, E, A, D, B
C) B, D, A, E, C
D) D, A, E, B, C
E) C, E, A, B, D
12) Sequencing (or dispatching):
A) assigns dates to specific jobs or operations steps.
B) assigns jobs to work centers.
C) specifies the order in which jobs should be done at each center.
D) assigns workers to jobs.
E) assigns workers to machines.
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
A) C, E, A, D, B
B) A, B, C, D, E
C) B, D, A, E, C
D) C, B, A, E, D
E) B, D, A, C, E
14) Flow time represents the time:
A) an order spends waiting for processing at a work center.
B) an order spends being processed at a work center.
C) an order spends moving from one work center to another.
D) to complete an order, including time spent in processing and in waiting.
E) none of the above
15) Which of the following dispatching rules tends to minimize job flow time?
A) FCFS: first come, first served
B) SPT: shortest processing time
C) EDD: earliest due date
D) LPT: longest processing time
E) FCLS: first come, last served
16) Average completion time for a schedule sequence at a work center is the ratio of:
A) total processing time to the number of jobs.
B) total flow time to total processing time.
C) total flow time to the number of jobs.
D) total processing time plus total late time to the number of jobs.
E) total flow time plus total late time to the number of jobs.
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 ________.
A) 100 percent; 10.625
B) low; .0941
C) 0.400 or 40 percent; 2.5
D) 0.235 or 23.5 percent; 4.25
E) maximized; minimized
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
A) B, D, A, E, C
B) C, D, A, B, E
C) C, E, A, D, B
D) E, B, A, D, C
E) B, D, A, C, E
19) Which critical ratio value implies that a job is already late?
A) more than 100
B) 1
C) less than 1
D) 10
E) 3.4
20) What is the priority rule that sequences jobs using the smallest ratio of due date from today to
processing time?
A) critical ratio
B) earliest due date
C) first come, first served
D) longest processing time
E) shortest processing time
21) Which of the following is an advantage of the FCFS dispatching rule when used in services?
A) FCFS maximizes utilization.
B) FCFS minimizes the average number of jobs in the system.
C) FCFS minimizes the average lateness of all jobs.
D) FCFS maximizes the number of jobs completed on time.
E) FCFS seems fair to customers.
22) What does the use of the shortest processing time sequencing rule generally produce?
A) maximum average lateness
B) maximum utilization
C) maximum effectiveness
D) minimum average flow time
E) B and D
23) When a set of jobs must pass through two workstations whose sequence is fixed, ________ is the
sequencing rule most commonly applied.
A) critical ratio
B) earliest due date
C) first come, first served
D) slack time remaining
E) Johnson's rule
