Deck 18: Management of Waiting Lines

Question 1

According to Little's Law, the number of people in line depends on the time of day that they arrive.

Answer 1

False

Question 2

An approach to reducing the variability in processing times might include greater standardization.

Answer 2

True

Question 3

The queuing models discussed in the text apply only to "steady state" conditions.Steady state exists only when customers arrive at a steady rate; that is, without any variability.

Answer 3

False

Question 4

In an infinite source model, the system utilization is the ratio of the arrival rate to the service capacity.

Question 5

For a system that has a low utilization ratio, decreasing service capacity slightly will have only negligible effect on customer waiting time.

Question 6

All infinite source queuing models require the system utilization to be less than 1.0.

Question 7

In an infinite source model, the average number being served is equal to the ratio of the arrival rate to the service rate.

Question 8

The point that minimizes total queuing system costs is that point where waiting costs and capacity costs are equal.

Question 9

A multiple channel system assumes that each server will have its own waiting line and line changing is not permitted.

Question 10

The most commonly used queuing models assume that the arrival rate can be described by a Poisson distribution.

Question 11

A system has one service facility that can service 10 customers per hour.The customers arrive at a variable rate, which averages 6 per hour.Since there is excess capacity, no waiting lines will form.

Question 12

The cost of customer waiting is easy to estimate, the number waiting multiplied by the wait cost per minute.

Question 13

In an infinite source model, the average time in line is equal to the average number in line divided by the arrival rate.

Question 14

To reduce the average number waiting in line, it is important to increase utilization.

Question 15

A Single Server, Variable Service Time is known as an M/D/1 system.

Question 16

A dental office with two professionals (one dentist, one hygienist) who work together as a team would be an example of a multiple channel system.

Question 17

Waiting lines occur even in under loaded systems because of variability in service rates and/or arrival rates.

Question 18

In a theme park like Disney world, reservation systems are a win-lose situation since only those holding reservations are satisfied.

Question 19

The goal of waiting line management is to eliminate customer waiting lines.

Question 20

The goal of queuing analysis is to balance the cost of providing a level of service capacity with the possible loss of business due to customers leaving the line or refusing to wait.

Question 21

The total cost curve:

A)Starts at zero and increases as service capacity increases.
B)Begins high and decreases as service capacity increases.
C)Starts high, declines, then increases again.
D)Remains relatively flat regardless of service capacity.
E)Starts at zero, increases rapidly, then declines slowly back to zero.

Question 22

Which of the following is not generally considered as a measure of system performance in a queuing analysis?

A)the average number waiting in line
B)the average number in the system
C)system utilization
D)the cost of servers plus customer waiting cost
E)average serving time

Question 23

A basic difference between infinite source and finite source queuing models is:

A)the number of servers
B)the average waiting time
C)the arrival distribution
D)size of potential calling population
E)processing rate

Question 24

A single phase queuing system is one which has a single:

A)channel
B)server
C)customer being served
D)operation
E)waiting line

Question 25

If variation in arrival and service rates can be reduced, waiting lines will be shortened.

Question 26

Why is there waiting in an infinite source queuing system?

A)poor scheduling of servers
B)slow service
C)low utilization
D)variability in arrival and service rates
E)multiple phase processing

Question 27

The goal of queuing analysis is to minimize:

A)the sum of customer waiting costs and capacity costs
B)the sum of customer waiting time and service time
C)capacity costs
D)customer waiting time
E)idle servers

Question 28

The finite-source queuing model is appropriate when the potential calling population is relatively large.

Question 29

Compared to a single channel system with exponential service time, the same system with a constant service time will have an average of one-half the number of customers waiting in the system.

Question 30

A single channel queuing system has an average service time of eight minutes and an average time between arrivals of 10 minutes.The arrival rate is:

A)6 per hour
B)7.5 per hour
C)8 per hour
D)10 per hour
E)12.5 per hour

Question 31

Little's Law states that the number of people in a waiting line is the average customer arrival rate multiplied by the ________.

A)average time in the system
B)average waiting time
C)service time minus the waiting time
D)average number in line
E)waiting time

Question 32

Balking is when customers grow impatient and leave a line.

Question 33

Compared to a single channel a system with exponential service time, a single channel system with a constant service time causes a reduction of 50 percent in the average number waiting in line.

Question 34

The goal of waiting line management is to minimize waiting time.

Question 35

If a manager increases system utilization (assuming no change in the customer arrival rate) what happens to the customer waiting time?

A)It increases exponentially.
B)It increases proportionally.
C)It decreases proportionally.
D)It decreases exponentially.
E)no change

Question 36

As the ratio of arrival rate to service rate is increased, which of the following is likely?

A)Customers move through the system in less time because utilization is increased.
B)Customers move through the system more slowly because utilization is increased.
C)Utilization is decreased because of the added strain on the system.
D)The average number in the system decreases.
E)There really is no change since arrival rates are offset by service rates.

Question 37

Queue discipline requires a security presence to maintain order.

Question 38

Servers, channels are described with many acronyms except _________.

A)M/P/S
B)M/M/1
C)M/D/1
D)M/M/S

Question 39

In a single-channel system, the utilization is equal to the arrival rate divided by the service rate.

Question 40

In a _______ system, customers enter the waiting line, receive service and leave.

A)Fast-track
B)Simulated
C)Queuing
D)Random
E)Non-random

Question 41

An alternative strategy to increase the capacity of a service system is:

A)Reducing the number of arrivals.
B)Increasing variability.
C)Increasing the processing rate.
D)Reducing the number of servers.
E)All of the above are viable options.

Question 42

What is average time in line for a high priority item?

Question 43

What is system utilization?

Question 44

A department has 5 machines that each run for an average of 8.4 hours (exponential) before service is required.Service time average is 1.6 hours (exponential).
(A) While running, each machine can produce 120 pieces per hour.With one server, what is the average hourly output actually achieved?
(B) With 2 servers, what is the probability that a machine would be served immediately when it requires service?
(C) If machine downtime cost is $100 per hour per machine, and server time costs $30 per hour, how many servers would be optimal?

Question 45

A ________ is one way of reducing perceived waiting time.

A)Bonus
B)Gatekeeper
C)Reservation
D)Diversion
E)Number calling system

Question 46

When the waiting cost incurred by customers likely varies, an appropriate queuing model is:

A)single channel, single phase
B)single channel, multiple phase
C)multiple channel, single priority
D)multiple channel, multiple phase
E)multiple channel, multiple priority

Question 47

A multiple channel queuing system with a Poisson arrival rate and exponential service time has an average arrival rate of 4 customers per hour and an average service time of 18 minutes per customer.The minimum number of servers required to avoid an overloaded system is:

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

Question 48

Two troubleshooters handle service calls for 10 machines.The average time between service requirements is 18 days, and service time averages 2 days.Assume exponential distributions.While running, each machine can produce 1,500 pieces per day.Determine:
(A) the percentage of time troubleshooters are idle
(B) each machine's net productivity
(C) If troubleshooters represent a cost of $150 per day, and machine downtime cost is $600 per day, would another troubleshooter be justified? Explain.

Question 49

A department has 5 semiautomatic pieces of equipment which operate for an average of 79 minutes before they must be reloaded.The reloading operation takes an average of 21 minutes per machine.Assume exponential distributions.
(A) What is the minimum number of servers needed to keep the average downtime per cycle to less than 25 minutes?
(B) If 1 server is used, what percentage of time will the machine be down?

Question 50

What is average time in line for a low priority item?

Question 51

A single channel queuing system has an average service time of 16 minutes per customer, which is exponentially distributed.The manager is thinking of converting to a system with a constant service time of 16 minutes.The arrival rate will remain the same.The effect will be to:

A)increase utilization
B)decrease utilization
C)increase the average waiting time
D)decrease the average waiting time
E)not have any effect since the service time is unchanged

Question 52

A single bay car wash with a Poisson arrival rate and an exponential service time has cars arriving an average of 10 minutes apart, and an average service time of four minutes.The system utilization is:

A).24
B).40
C).67
D)2.50
E)none of these

Question 53

A multiple channel system has customers arriving at an average rate of five per hour and an average service time of forty minutes.The minimum number of servers for this system to be under loaded is:

A)2
B)3
C)4
D)5
E)none of these

Question 54

During the early morning hours, customers arrive at a branch post office at an average rate of 45 per hour (Poisson), while clerks can handle transactions in an average time (exponential) of 4 minutes each.Find:
(A) the average number of customers waiting for service if 6 clerks are used
(B) the minimum number of clerks needed to keep the average time in the system to under 5 minutes
(C) If clerk cost is $30 per hour and customer waiting time represents a "cost" of $20 per hour, how many clerks can be justified on a cost basis?

Question 55

Customers arrive at a video rental desk at the rate of one per minute (Poisson).Each server can handle 0.40 customers per minute (Poisson).
(A) If there are four servers, determine:
(1) The average time it takes to rent a video tape
(2) The probability of three or fewer customers in the system
(B) What is the minimum number of servers needed to achieve an average time in the system of less than three minutes?

Question 56

Which one of the following measures of system performance is a key measure with respect to customer satisfaction?

A)average number of customers waiting in line
B)system utilization
C)average number of customer in the calling population
D)probability of a server being busy
E)capacity costs per hour

Question 57

What is the overall average arrival rate?

Question 58

Customers arrive at a suburban ticket outlet at the rate of 14 per hour on Monday mornings.This can be described by a Poisson distribution.Selling the tickets and providing general information takes an average of 3 minutes per customer, and varies exponentially.There is 1 ticket agent on duty on Mondays.Determine each of the following:
(A) system utilization
(B) average number in line
(C) average time in line
(D) average time in the system

Question 59

A queuing system has four crews with three members each.The number of "servers" is:

A)3
B)4
C)7
D)12
E)1

Question 60

Customers filter into a record shop at an average of 1 per minute (Poisson) where the service rate is 15 per hour (Poisson).
Determine the following:
(A) the average number of customers in the system with 8 servers
(B) the minimum number of servers needed to keep the average time in the system to under 6 minutes

Question 61

Which of the following would reduce perceived waiting times most dramatically in a doctor's office?

A)putting all clocks out of sight
B)removing couches
C)having the patient fill out forms
D)implementing a "no-cell-phone" policy
E)keeping expected waiting times from the patients

Question 62

A manager assembled the following information about an infinite source waiting line system: 5 servers, an arrival rate of 6 per hour, and a service time of 20 minutes.The manager has determined that the average number of customers waiting for service is 0.04.Determine each of the following:
(A) the system utilization
(B) the average waiting time in line in minutes
(C) the average time in the system
(D) the average number in the system

Question 63

What is the average time that parties without player's cards wait to be seated?

A)approx.4 minutes
B)approx.8 minutes
C)approx.12 minutes
D)approx.15 minutes
E)approx.2 minutes

Question 64

What is the average number of high priority items waiting in line for service?

Question 65

What is average time in the system for a high priority item?

Question 66

What is the average machine downtime with two operators?

A)1.71 minutes
B)3.46 minutes
C)6.25 minutes
D)7.71 minutes
E)9.46 minutes

Question 67

What is the probability that a machine will have to wait for service with two operators?

A).654
B).090
C).346
D).910
E).016

Question 68

Offering an "early bird" special at a restaurant to reduce waiting times during peak hours is an example of ____________.

A)demand shifting
B)queuing psychology
C)service phasing
D)service standardization
E)outsourcing

Question 69

If a firm has reached the point at which further reducing waiting time is not economically feasible, reducing the ______________ is sometimes attractive.

A)channels
B)perceived service time
C)capacity underload
D)perceived waiting time
E)system underutilization

Question 70

What is the average number of machines down with one operator?

A)1.49
B)3.35
C)4.40
D)6.65
E)8.51

Question 71

What is the average number of all items waiting in line for service?

Question 72

How many spaces should be provided to have a 96% probability of accommodating all of the waiting cars?

A)10
B)11
C)12
D)13
E)14

Question 73

What is the average number of low priority items waiting in line for service?

Question 74

A restaurant that implements a limited menu and a "no substitutions" policy during peak dining hours is practicing _____________ with respect to waiting line management.

A)demand shifting
B)queuing psychology
C)service standardization
D)service phasing
E)outsourcing

Question 75

What is the average time that player's card holders wait to be seated?

A)approx.4 minutes
B)approx.8 minutes
C)approx.12 minutes
D)approx.15 minutes
E)approx.2 minutes

Question 76

If operators cost $15 per hour in wages and fringe benefits and machine downtime costs $75 per hour in lost production, what is the optimal number of operators for this bank of machines?

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

Question 77

On average, how much longer do parties without player's cards spend in the system, compared to parties with the player's cards?

A)2 minutes
B)4 minutes
C)8 minutes
D)10 minutes
E)It is impossible to say without more information.

Question 78

On average, how many parties with player's cards are waiting to be seated?

A)0.52
B)0.41
C)0.88
D)1.23
E)1.75

Question 79

On average, how many parties without player's cards are waiting to be seated?

A)0.52
B)0.41
C)0.88
D)1.23
E)1.75

Question 80

What is average time in the system for a low priority item?