Chapter C  Waiting Lines

Supplement

C / Waiting Lines

TRUE/FALSE

  1. Waiting lines cannot develop if the time to process a customer is constant.

Answer: False

Reference: Why Waiting Lines Form

Difficulty: Easy

Keywords: waiting, line, customers

  1. The four elements common to all waiting-line situations are a customer population, a waiting line of customers, the service facility, and a priority rule.

Answer: True

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: priority, rule, customer, line, population

  1. A phase represents a single step in providing a service.

Answer: True

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: phase, service

  1. A bank that dedicates one window for commercial account customers and one window for personal account channel has two channels.

Answer: True

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: queue, channel

  1. If the service system generates customers according to a Poisson distribution, the exponential distribution describes the probability that the next customer will arrive in the next T time periods.

Answer: True

Reference: Probability Distributions

Difficulty: Moderate

Keywords: Poisson, exponential, distribution

  1. The mean of the Poisson distribution is equal to its standard deviation.

Answer: False

Reference: Probability Distributions

Difficulty: Moderate

Keywords: Poisson, distribution, mean, variance

  1. Short queue lengths typically mean not enough capacity.

Answer: False

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Easy

Keywords: queue, capacity, length

  1. The number of customers in queue and being served also relates to service efficiency and capacity.

Answer: True

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate

Keywords: customer, queue, capacity, efficiency

  1. Long lines always mean long waiting times.

Answer: False

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate

Keywords: line, waiting, time

  1. It is impossible for management to affect the rate of customer arrivals.

Answer: False

Reference: Decision Areas for Management

Difficulty: Moderate

Keywords: arrival, rate, affect

  1. Management, servers, and customers would all be happy if, in a single-server situation, the parameter µ is much greater than λ.

Answer: True

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate

Keywords: single, server, arrival, service, rate

MULTIPLE CHOICE

  1. Which of the following is LEAST likely to benefit from waiting line analysis?
  2. Capacity planning
  3. Inventory management
  4. Budget planning
  5. Scheduling

Answer:c

Reference: Uses of Waiting-Line Theory

Difficulty: Moderate

Keywords: single, server, service, rate

  1. The best example of a finite customer population is:
  2. the car-buying public of an automotive manufacturer.
  3. the constituents in a precinct lining up to vote.
  4. the e-mail messages arriving at a major ISP mail server.
  5. the members of the Management department at your university waiting to speak to the Dean about their department chairman.

Answer:d

Reference: Structure of Waiting-Line Problems

Difficulty: Easy

Keywords: customer, population, finite

  1. The distinction between an infinite customer population and a finite customer population is:
  2. whether the potential number of customers is appreciably affected by the number of customers already in the system.
  3. whether the number of potential customers exceeds the square of the number of servers.
  4. whether the number of potential customers exceeds the number of servers raised to the power of the number of channels.
  5. if the number of customers exceeds infinity.

Answer:a

Reference: Structure of Waiting-Line Problems

Difficulty: Easy

Keywords: customer, population, finite

  1. Ed Deadbeat races to the Bursar’s Office on the first day of class and notes that the line is four students long. Ed figures that the wait will be at least ten minutes and, having better uses of his time, he decides to proceed to the next item on his to-do list. Ed’s behavior is best described as:
  2. reneging.
  3. balking.
  4. blocking.
  5. queuing.

Answer:b

Reference: Structure of Waiting-Line Problems

Difficulty: Easy

Keywords: balking, balk

  1. India Sisson wants to grab a latte before heading to her marketing class, knowing that the jolt of a double tall mocha is the only thing that can possibly keep her eyes open during today’s presentation on the four P’s. The barista is slower than molasses in January and India notes that the pace of the line won’t permit her to grab her favorite seat in the back row of her class. She decides to risk marketing without a latte and leaves the line before getting served. India’s behavior is best described as:
  2. balking.
  3. blocking.
  4. reneging.
  5. queuing.

Answer:c

Reference: Structure of Waiting-Line Problems

Difficulty: Easy

Keywords: reneging, renege

  1. The single, multiple, and finite queuing models all assume that:
  2. the arrival rate exceeds the service rate..
  3. the number of servers exceeds the number of customers.
  4. the number of customers exceeds the number of servers.
  5. the customers are patient.

Answer:d

Reference: Structure of Waiting-Line Problems

Difficulty: Easy

Keywords: reneging, renege, balking, balk, patient

  1. An automatic, drive-through car wash is an example of a:
  2. single-channel, single-phase arrangement.
  3. single-channel, multiple-phase arrangement.
  4. multiple-channel, single-phase arrangement.
  5. multiple-channel, multiple-phase arrangement.

Answer: a

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: single, channel, phase

  1. A drive-through system at a fast food restaurant where the first facility takes the order, the second takes the money, and the third provides the food is an example of:
  2. single-channel, single-phase arrangement.
  3. single-channel, multiple-phase arrangement.
  4. multiple-channel, single-phase arrangement.
  5. multiple-channel, multiple-phase arrangement.

Answer: b

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: single, channel, multiple, phase

  1. A bank lobby with six teller windows, each with a separate line, is an example of a:
  2. single-channel, single-phase arrangement.
  3. single-channel, multiple-phase arrangement.
  4. multiple-channel, single-phase arrangement.
  5. multiple-channel, multiple-phase arrangement.

Answer: c

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: multiple, channel, single, phase

  1. A Laundromat where there are washing machines and dryers is an example of a:
  2. single-channel, single-phase arrangement.
  3. single-channel, multiple-phase arrangement.
  4. multiple-channel, single-phase arrangement.
  5. multiple-channel, multiple-phase arrangement.

Answer: d

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: multiple, channel, phase

  1. A super computer-accessory discount store often has customers who leave the checkout line before being served because of excessive waiting times. The store has a(n):
  2. infinite customer population with balking customers.
  3. infinite customer population with reneging customers.
  4. finite customer population with balking customers.
  5. finite customer population with reneging customers.

Answer: b

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: infinite, customer, balk

  1. A homemade-ice cream shop owner has noticed that, often, potential customers will stop outside the store, assess the wait in line, and then pass by. The shop has a(n):
  2. infinite customer population with balking customers.
  3. infinite customer population with reneging customers.
  4. finite customer population with balking customers.
  5. finite customer population with reneging customers.

Answer: a

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: customer, balk, infinite, population

  1. The owner of a desktop publishing company has seven loyal clients who periodically require his services. The owner has:
  2. an infinite customer population of patient customers.
  3. an infinite population of impatient customers.
  4. a finite customer population.
  5. a finite customer population with balking customers.

Answer: c

Reference: Structure of Waiting-Line Problems

Difficulty: Moderate

Keywords: finite, customer, population

  1. Customers arrive according to a Poisson distribution. The average number of customer arrivals per hour is four. The probability that three customers will arrive in the next two hours is:
  2. less than or equal to 0.015.
  3. greater than 0.015 but less than or equal to 0.020.
  4. greater than 0.020 but less than or equal to 0.025.
  5. greater than 0.025.

Answer: d

Reference: Probability Distributions

Difficulty: Moderate

Keywords: probability, customer, arrival

  1. Customers arrive according to a Poisson distribution. The average number of customer arrivals per hour is six. The probability that four customers will arrive in the next three hours is:
  2. less than or equal to 0.01.
  3. greater than 0.01 but less than or equal to 0.02.
  4. greater than 0.02 but less than or equal to 0.03.
  5. greater than 0.03.

Answer: a

Reference: Probability Distributions

Difficulty: Moderate

Keywords: arrival, probability

  1. Customers arrive according to a Poisson distribution. The average number of customer arrivals per hour is three. The probability that four customers will arrive in the next two hours is:
  2. less than or equal to 0.10.
  3. greater than 0.10 but less than or equal to 0.12.
  4. greater than 0.12 but less than or equal to 0.14.
  5. greater than 0.14.

Answer: c

Reference: Probability Distributions

Difficulty: Moderate

Keywords: arrival, probability

  1. Customers arrive according to a Poisson distribution. The average number of customer arrivals per hour is two. The probability that five customers will arrive in the next three hours is:
  2. less than or equal to 0.10.
  3. greater than 0.10 but less than or equal to 0.12.
  4. greater than 0.12 but less than or equal to 0.14.
  5. greater than 0.14.

Answer: d

Reference: Probability Distributions

Difficulty: Moderate

Keywords: probability, arrival

  1. Customers are serviced at a rate of four customers per hour according to an exponential distribution. What is the probability that customer service will require fewer than 30 minutes?
  2. Less than or equal to 0.50
  3. Greater than 0.50 but less than or equal to 0.60
  4. Greater than 0.60 but less than or equal to 0.70
  5. Greater than 0.70

Answer: d

Reference: Probability Distributions

Difficulty: Moderate

Keywords: service, rate, probability

  1. Customers are serviced at a rate of six customers per hour according to an exponential distribution. What is the probability that customer service will require fewer than 20 minutes?
  2. Less than or equal to 0.70
  3. Greater than 0.70 but less than or equal to 0.80
  4. Greater than 0.80 but less than or equal to 0.90
  5. Greater than 0.90

Answer: c

Reference: Probability Distributions

Difficulty: Moderate

Keywords: service, rate, probability

  1. Customers are serviced at a rate of three customers per hour according to an exponential distribution. What is the probability that customer service will require fewer than 10 minutes?
  2. Less than or equal to 0.40
  3. Greater than 0.40 but less than or equal to 0.45
  4. Greater than 0.45 but less than or equal to 0.50
  5. Greater than 0.50

Answer: a

Reference: Probability Distributions

Difficulty: Moderate

Keywords: customer, service, rate, probability

  1. Customers are serviced at a rate of five customers per hour according to an exponential distribution. What is the probability that customer service will require fewer than 20 minutes?
  2. Less than or equal to 0.75
  3. Greater than 0.75 but less than or equal to 0.80
  4. Greater than 0.80 but less than or equal to 0.85
  5. Greater than 0.85

Answer: c

Reference: Probability Distributions

Difficulty: Moderate

Keywords: customer, service, rate, probability

  1. Customers are serviced at a rate of 10 customers per hour according to an exponential distribution. What is the probability that customer service will require fewer than two minutes?
  2. Less than or equal to 0.25
  3. Greater than 0.25 but less than or equal to 0.30
  4. Greater than 0.30 but less than or equal to 0.35
  5. Greater than 0.35

Answer: b

Reference: Probability Distributions

Difficulty: Moderate

Keywords: customer, service, rate, probability

  1. With a single-server model, increasing the service rate while holding all other factors constant will:
  2. increase the utilization of the server.
  3. increase the time spent per customer.
  4. decrease the probability that there are two customers in the system at any time.
  5. decrease the arrival rate of customers.

Answer: c

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate

Keywords: single, server, service, rate

  1. With a single-server model, increasing the promotions for a service through advertising will most likely:
  2. increase the utilization of the server.
  3. decrease the average number of customers in the service system.
  4. decrease the average time a customer spends in the system.
  5. increase the probability that the server will be idle.

Answer: a

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: single, server, utilization, arrival, rate

  1. With a single-server model, increasing the capital-to-labor ratio will most likely:
  2. increase the utilization of the server.
  3. have no effect on the operating characteristics because they are affected only by work-methods changes.
  4. decrease the probability that there are zero customers in the system at any time.
  5. decrease the average number of customers in the waiting line.

Answer: d

Reference: Multiple sections

Difficulty: Hard

Keywords: single, server, capital, labor, length

  1. With a single-server model, increasing the arrival rate by 10 percent and also increasing the service rate by 10 percent will result in:
  2. an increase in the utilization of the server.
  3. an increase in the average number of customers in the system.
  4. a decrease in the average time spent in the system, including service.
  5. an increase in the waiting-line time.

Answer: c

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: single, server, arrival, service, rate

  1. With a single-server model, increasing the arrival rate by 10 percent and also increasing the service rate by 10 percent will result in:
  2. a decrease in the utilization of the server.
  3. no change in the average number of customers in the service system.
  4. an increase in the average number of customers in the waiting line.
  5. an increase in the waiting time in line.

Answer: b

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: single, server, arrival, service, rate

  1. With a single-server model, increasing the arrival rate by 10 percent and also increasing the service rate by 10 percent will result in:
  2. no change in the probability that there are n customers in the system.
  3. a decrease in the average waiting time in line.
  4. an increase in the average time spent in the system, including service.
  5. an increase in the average number of customers in the system.

Answer: a

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: single, server, arrival, service, rate

  1. With a multiple-server model, increasing the arrival rate by 10 percent and also increasing the service rate of each server by 10 percent will result in:
  2. a decrease in the utilization of the system.
  3. no change in the average number of customers in the waiting line.
  4. a decrease in the average number of customers in the waiting line.
  5. an increase in the waiting time in line.

Answer: b

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: multiple, server, arrival, service, rate, queue, length

  1. With a finite-source model, increasing the arrival rate by 10 percent and also increasing the service rate by 10 percent will result in:
  2. an increase in the utilization of the server.
  3. an increase in the average number of customers in the service system.
  4. a decrease in the average time spent in the system, including service.
  5. an increase in the waiting time in line.

Answer: c

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: finite, source, arrival, rate, service

  1. With a finite-source model, increasing the arrival rate by 10 percent and also increasing the service rate by 10 percent will result in:
  2. a decrease in the utilization of the server.
  3. no change in the average number of customers in the system.
  4. an increase in the average number of customers in the waiting line.
  5. an increase in the waiting time in line.

Answer: b

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Hard

Keywords: finite, source, arrival, rate, service

  1. In the single-server model:
  2. customers are assumed to arrive at constant intervals of time.
  3. the variability of customer arrivals is most often described by a Poisson distribution.
  4. the mean of the distribution of customer arrivals must be greater than the variance of customer arrivals to get meaningful results.
  5. the probability of n arrivals in T time periods comes from a normal distribution.

Answer: b

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate

Keywords: Poisson, single, server, arrival

  1. In the single-server model:
  2. the service time of a customer is most often described by an exponential distribution.
  3. the service time depends on the number of customers in the system as long as there is at least one customer in the waiting line.
  4. the mean of the service-time distribution must be as great as the target service time for a feasible solution.
  5. service times are always constant to avoid large waiting lines.

Answer: a

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate

Keywords: single, server, exponential, distribution

  1. In order to have equivalent performance on average waiting time in a single server model, an increase in interarrival time must be accompanied by:
  2. an increase in µ.
  3. an increase in the number of servers.
  4. an increase in the number of channels.
  5. an increase in the line length.

Answer: a

Reference: Using Waiting Line Models to Analyze Operations

Difficulty: Moderate

Keywords: phase

  1. Use the information in Scenario C.1. What is the utilization of the ticket taker?
  2. 0.66
  3. 0.55
  4. 0.44
  5. 0.33

Answer: a

Reference: Using Waiting-Line Models to Analyze Operations

Difficulty: Moderate