MANSCI. Chapter 9-12

A path through a project network must reach every node.

FALSE

A waiting line situation where every customer waits in the same line before being served by the same server is called a single server waiting line.

FALSE

Crashing refers to an unanticipated delay in a critical path activity that causes the total time to exceed its limit.

FALSE

Critical activities are those that can be delayed without delaying the entire project

FALSE

For all waiting lines, P0 + Pw = 1.

FALSE

For an M/M/1 queuing system, if the service rate, µ, is doubled, the average wait in the system, W, is cut in half.

FALSE

If an item's per-unit backorder cost is greater than its per-unit holding cost, no intentional shortage should be planned.

FALSE

If some maximum number of customers is allowed in a queuing system at one time, the system has a finite calling population

FALSE

In a multiple channel system it is more efficient to have a separate waiting line for each channel.

FALSE

Little's flow equations indicate that the relationship of L to Lq is the same as that of W to Wq.

FALSE

PERT and CPM are applicable only when there is no dependence among activities.

FALSE

Periodic review systems require smaller safety stock levels than corresponding continuous review systems.

FALSE

Queue discipline refers to the assumption that a customer has the patience to remain in a slow moving queue

FALSE

The cost of overestimating demand is usually harder to determine than the cost of underestimating demand.

FALSE

The earliest start time for an activity is equal to the smallest of the earliest finish times for all its immediate predecessors.

FALSE

The latest finish time for an activity is the largest of the latest start times for all activities that immediately follow the activity.

FALSE

The terms "inventory on hand" and "inventory position" have the same meaning.

FALSE

The time between placing orders is the lead time.

FALSE

The variance in the project completion time is the sum of the variances of all activities in the project.

FALSE

To be considered as inventory, goods must be finished and waiting for delivery.

FALSE

Use of the Poisson probability distribution assumes that arrivals are not random

FALSE

Waiting line models describe the transient-period operating characteristics of a waiting line

FALSE

When a waiting system is in steady-state operation, the number of units in the system is not changing.

FALSE

When activity times are uncertain, an activity's most likely time is the same as its expected time.

FALSE

When quantity discounts are available, order an amount from the highest discount category.

FALSE

A critical activity can be part of a noncritical path.

TRUE

Adding more channels always improves the operating characteristics of the waiting line and reduces the waiting cost.

TRUE

Before waiting lines can be analyzed economically, the arrivals' cost of waiting must be estimated.

TRUE

Constant demand is a key assumption of the EOQ model.

TRUE

Constraints in the LP models for crashing decisions are required to compare the activity's earliest finish time with the earliest finish time of each predecessor.

TRUE

For a single-channel waiting line, the utilization factor is the probability that an arriving unit must wait for service.

TRUE

If service time follows an exponential probability distribution, approximately 63% of the service times are less than the mean service time.

TRUE

If the optimal production lot size decreases, average inventory increases

TRUE

In developing the total cost for a waiting line, waiting cost takes into consideration both the time spent waiting in line and the time spent being served.

TRUE

In the EOQ model, the average inventory per cycle over many cycles is Q/2.

TRUE

In the periodic review model, the order quantity at each review period must be sufficient to cover demand for the review period plus the demand for the following lead time.

TRUE

In waiting line systems where the length of the waiting line is limited, the mean number of units entering the system might be less than the arrival rate.

TRUE

Queue discipline refers to the manner in which waiting units are arranged for service

TRUE

The EOQ model is insensitive to small variations or errors in the cost estimates.

TRUE

The earliest finish time for the final activity is the project duration.

TRUE

The length of time an activity can be delayed without affecting the project completion time is the slack.

TRUE

The linear programming model for crashing presented in the textbook assumes that any portion of the activity crash time can be achieved for a corresponding portion of the activity crashing cost.

TRUE

The project manager should monitor the progress of any activity with a large time variance even if the expected time does not identify the activity as a critical activity.

TRUE

The single-period inventory model is most applicable to items that are perishable or have seasonal demand.

TRUE

When activity times are uncertain, total project time is normally distributed with mean equal to the sum of the means of all of the critical activities.

TRUE

When blocked customers are cleared, an important decision is how many channels to provide.

TRUE

When demand is independent, it is not related to demand for other components or items produced by the firm.

TRUE

When there is probabilistic demand in a multi-period model, the inventory level will not decrease smoothly and can fall below 0.

TRUE

What queue discipline is assumed by the waiting line models presented in the textbook? a. first-come first-served. b. last-in first-out. c. shortest processing time first. d. No discipline is assumed.

a. first-come first-served.

Activities K, M and S immediately follow activity H, and their latest start times are 14, 18, and 11. The latest finish time for activity H a. is 11. b. is 14. c. is 18. d. cannot be determined.

a. is 11.

Inventory a. is held against uncertain usage so that a supply of items is available if needed. b. constitutes a small part of the cost of doing business. c. is not something that can be managed effectively. d. All of the alternatives are correct.

a. is held against uncertain usage so that a supply of items is available if needed.

The manner in which units receive their service, such as FCFS, is the a. queue discipline. b. channel. c. steady state. d. operating characteristic.

a. queue discipline.

A simulation model uses the mathematical expressions and logical relationships of the a. real system. b. computer model. c. performance measures. d. estimated inferences.

a. real system.

A firm that is presently using the Economic Order Quantity model and is planning to switch to the Economic Production Lot-Size model can expect a. the Q* to increase. b. the maximum inventory level to increase. c. the order cycle to decrease. d. annual holding cost to be less than annual setup cost

a. the Q* to increase.

For an activity with more than one immediate predecessor activity, which of the following is used to compute its earliest finish (EF) time? a. the largest EF among the immediate predecessors. b. the average EF among the immediate predecessors. c. the largest LF among the immediate predecessors. d. the difference in EF among the immediate predecessors

a. the largest EF among the immediate predecessors.

For inventory systems with constant demand and a fixed lead time, a. the reorder point = lead-time demand. b. the reorder point > lead-time demand. c. the reorder point < lead-time demand. d. the reorder point is unrelated to lead-time demand

a. the reorder point = lead-time demand.

If arrivals occur according to the Poisson distribution every 20 minutes, then which is NOT true? a. λ = 20 arrivals per hour b. λ = 3 arrivals per hour c. λ = 1/20 arrivals per minute d. λ = 72 arrivals per day

a. λ = 20 arrivals per hour

Operating characteristics formulas for the single-channel queue do NOT require a. λ ≥ µ. b. Poisson distribution of arrivals. c. an exponential distribution of service times. d. an FCFS queue discipline.

a. λ ≥ µ.

Which of the following is a general rule for crashing activities? a. Crash only non-critical activities. b. Crash activities with zero slack. c. Crash activities with the greatest number of predecessors. d. Crash the path with the fewest activities.

b. Crash activities with zero slack.

Slack equals a. LF − EF. b. EF − LF. c. EF − LS. d. LF − ES.

b. EF − LF.

The maximum inventory with backorders is a. Q b. Q − S c. S d. (Q − S) / 2

b. Q − S

Which is not a significant challenge of project scheduling? a. deadlines exist. b. activities are independent. c. many employees could be required. d. delays are costly

b. activities are independent.

Little's flow equations a. require Poisson and exponential assumptions. b. are applicable to any waiting line model. c. require independent calculation of W, L, Wq, and Lq. d. All of the alternatives are correct.

b. are applicable to any waiting line model.

When activity times are uncertain, a. assume they are normally distributed. b. calculate the expected time, using (a + 4m + b)/6. c. use the most likely time. d. calculate the expected time, using (a + m + b)/3.

b. calculate the expected time, using (a + 4m + b)/6.

The earliest start time rule a. compares the starting times of all activities for successors of an activity. b. compares the finish times for all immediate predecessors of an activity. c. determines when the project can begin. d. determines when the project must begin.

b. compares the finish times for all immediate predecessors of an activity.

The EOQ model a. determines only how frequently to order. b. considers total cost. c. minimizes both ordering and holding costs. d. All of the alternatives are correct.

b. considers total cost.

Inventory models in which the rate of demand is constant are called a. fixed models. b. deterministic models. c. JIT models. d. requirements models.

b. deterministic models.

In a multiple channel system a. each server has its own queue. b. each server has the same service rate. c. µ > λ d. All of the alternatives are correct

b. each server has the same service rate.

Activities following a node a. can begin as soon as any activity preceding the node has been completed. b. have an earliest start time equal to the largest of the earliest finish times for all activities entering the node. c. have a latest start time equal to the largest of the earliest finish times for all activities entering the node. d. None of the alternatives is correct.

b. have an earliest start time equal to the largest of the earliest finish times for all activities entering the node.

Arcs in a project network indicate a. completion times. b. precedence relationships. c. activities. d. the critical path.

b. precedence relationships.

Periodic review inventory systems a. are less subject to stockouts than corresponding continuous review systems. b. require larger safety stock levels than corresponding continuous review systems. c. have constant order quantities. d. make the coordination of orders for multiple products more difficult.

b. require larger safety stock levels than corresponding continuous review systems.

Decision makers in queuing situations attempt to balance a. operating characteristics against the arrival rate. b. service levels against service cost. c. the number of units in the system against the time in the system. d. the service rate against the arrival rate.

b. service levels against service cost.

Which cost would not be considered part of a holding cost? a. cost of capital b. shipping cost c. insurance cost d. warehouse overhead

b. shipping cost

The definition of service level used in this chapter is a. the percentage of all demand that can be satisfied from inventory. b. the percentage of all order cycles that do not experience a stockout. c. the percentage of demand during the lead-time period that can be satisfied from inventory. d. None of the alternatives is correct

b. the percentage of all order cycles that do not experience a stockout.

The assumption of exponentially distributed service times indicates that a. 37% of the service times are less than the mean service time. b. 50% of the service times are less than the mean service time. c. 63% of the service times are less than the mean service time. d. service time increase at an exponential rate as the waiting line grows.

c. 63% of the service times are less than the mean service time.

For the EOQ model, which of the following relationships is incorrect? a. As the order quantity increases, the number of orders placed annually decreases. b. As the order quantity increases, annual holding cost increases. c. As the order quantity increases, annual ordering cost increases. d. As the order quantity increases, average inventory increases.

c. As the order quantity increases, annual ordering cost increases.

Which of the following is always true about a critical activity? a. LS = EF. b. LF = LS. c. ES = LS. d. EF = ES.

c. ES = LS.

For the inventory model with planned shortages, the optimal order quantity results in a. annual holding cost = annual ordering cost. b. annual holding cost = annual backordering cost. c. annual ordering cost = annual holding cost + annual backordering cost. d. annual ordering cost = annual holding cost − annual backordering cost.

c. annual ordering cost = annual holding cost + annual backordering cost.

Values for the probabilistic inputs to a simulation a. are selected by the decision maker. b. are controlled by the decision maker. c. are randomly generated based on historical information. d. are calculated by fixed mathematical formulas

c. are randomly generated based on historical information.

Safety stock a. can be determined by the EOQ formula. b. depends on the inventory position. c. depends on the variability of demand during lead time. d. is not needed if Q* is the actual order quantity.

c. depends on the variability of demand during lead time.

Activities G, P, and R are the immediate predecessors for activity W. If the earliest finish times for the three are 12, 15, and 10, then the earliest start time for W a. is 10. b. is 12. c. is 15. d. cannot be determined.

c. is 15.

Activities with zero slack a. can be delayed. b. must be completed first. c. lie on a critical path. d. have no predecessors.

c. lie on a critical path.

The economic production lot size model is appropriate when a. demand exceeds the production rate. b. there is a constant supply rate for every period, without pause. c. ordering cost is equivalent to the production setup cost. d. All of the alternatives are correct.

c. ordering cost is equivalent to the production setup cost.

In the single-period inventory model with probabilistic demand, a. surplus items are not allowed to be carried in future inventory. b. co = cu. c. probabilities are used to calculate expected losses. d. All of the alternatives are correct.

c. probabilities are used to calculate expected losses.

Inventory position is defined as a. the amount of inventory on hand in excess of expected demand. b. the amount of inventory on hand. c. the amount of inventory on hand plus the amount of inventory on order. d. None of the alternatives is correct.

c. the amount of inventory on hand plus the amount of inventory on order.

Which of the following can NOT be found by the queuing formulas presented in the textbook? a. the probability that no units are in the system. b. the average number of units in the system. c. the maximum time a unit spends in the system. d. the average time a unit spends in the system.

c. the maximum time a unit spends in the system.

Annual purchase cost is included in the total cost in a. the EOQ model. b. the economic production lot size model. c. the quantity discount model. d. all inventory models.

c. the quantity discount model.

Models with a finite calling population a. have an arrival rate independent of the number of units in the system. b. have a service rate dependent on the number of units in the system. c. use the size of the population as a parameter in the operating characteristics formulas. d. All of the alternatives are correct.

c. use the size of the population as a parameter in the operating characteristics formulas.

In a waiting line situation, arrivals occur, on average, every 10 minutes, and 10 units can be received every hour. What are λ and µ? a. λ = 10, µ = 10 b. λ = 6, µ = 6 c. λ = 6, µ = 10 d. λ = 10, µ = 6

c. λ = 6, µ = 10

To determine how to crash activity times a. normal activity costs and costs under maximum crashing must be known. b. shortest times with crashing must be known. c. realize that new paths may become critical. d. All of the alternatives are true.

d. All of the alternatives are true.

Which of the following is not implied when average inventory is Q/2, where Q is the order quantity? a. An entire order quantity arrives at one time. b. The previous order quantity is entirely depleted when the next order arrives. c. An order quantity is depleted at a uniform rate over time. d. Backorders are permitted.

d. Backorders are permitted.

For many waiting line situations, the arrivals occur randomly and independently of other arrivals and it has been found that a good description of the arrival pattern is provided by a. a normal probability distribution. b. an exponential probability distribution. c. a uniform probability distribution. d. a Poisson probability distribution.

d. a Poisson probability distribution.

In deciding which activities to crash, one must a. crash all critical activities. b. crash largest-duration activities. c. crash lowest-cost activities. d. crash activities on the critical path(s) only.

d. crash activities on the critical path(s) only.

PERT and CPM a. are most valuable when a small number of activities must be scheduled. b. have different features and are not applied to the same situation. c. do not require a chronological relationship among activities. d. have been combined to develop a procedure that uses the best of each.

d. have been combined to develop a procedure that uses the best of each.

The critical path a. is any path that goes from the starting node to the completion node. b. is a combination of all paths. c. is the shortest path. d. is the longest path.

d. is the longest path.

The objective of the EOQ with quantity discounts model is to a. determine the minimum order quantity required for the maximum discount. b. balance annual ordering and holding costs. c. minimize annual purchase cost. d. minimize the sum of annual carrying, holding, and purchase costs.

d. minimize the sum of annual carrying, holding, and purchase costs.

Performance measures dealing with the number of units in line and the time spent waiting are called a. queuing facts. b. performance queues. c. system measures. d. operating characteristics.

d. operating characteristics.

For an activity with more than one immediate successor activity, its latest-finish time is equal to the a. largest latest-finish time among its immediate successors. b. smallest latest-finish time among its immediate successors. c. largest latest-start time among its immediate successors. d. smallest latest-start time among its immediate successors.

d. smallest latest-start time among its immediate successors.

The total cost for a waiting line does NOT specifically depend on a. the cost of waiting. b. the cost of service. c. the number of units in the system. d. the cost of a lost customer.

d. the cost of a lost customer.

The arrival rate in queuing formulas is expressed as a. the mean time between arrivals. b. the minimum number of arrivals per time period. c. the mean number of arrivals per channel. d. the mean number of arrivals per time period.

d. the mean number of arrivals per time period.