ISDS Exam2 Module D Essay Jacob Herring
question

1. Waiting-line models are useful to operations in such diverse settings as service systems, maintenance activities, and shop-floor control.

True (Introduction, easy)
question

2. The two characteristics of the waiting line itself are whether its length is limited or unlimited and the discipline of the people or items in it.

True (Characteristics of a waiting-line system, easy)
question

3. A waiting-line system has three parts: the size of the arrival population, the behavior of arrivals, and the statistical distribution of arrivals.

False (Characteristics of a waiting-line system, easy)
question

4. A copy center has five machines that serve many customers throughout the day; the waiting-line system for copy service has an infinite population while the waiting-line system for copier maintenance has a finite population

True (Characteristics of a waiting-line system, easy)
question

5. In queuing problems, arrival rates are generally described by the normal probability distribution.

False (Characteristics of a waiting-line system, moderate)
question

6. Balk and renege are elements of queue discipline.

False (Characteristics of a waiting-line problem, easy)
question

7. A hospital emergency room always follows a first-in, first-served queue discipline in the interest of fairness.

False (Characteristics of a waiting-line system, moderate)
question

8. In queuing problems, the term “renege” refers to the fact that some customers leave the queue before service is completed.

True (Characteristics of a waiting-line system, moderate)
question

9. A waiting-line system with one waiting line and three sequential processing stages is a multichannel single-phase system.

False (Characteristics of a waiting-line problem, easy)
question

10. If the service time within a queuing system is constant, the service rate can be easily described by a negative exponential distribution.

False (Characteristics of a waiting-line system, moderate)
question

11. The cost of waiting decreases as the service level increases.

True (Queuing costs, moderate)
question

12. LIFS (last-in, first-served) is a common queue discipline, most often seen where people, not objects, form the waiting line.

False (Characteristics of a waiting-line problem, moderate)
question

13. A bank office with five tellers, each with a separate line of customers, exhibits the characteristics of a multi-phase queuing system.

False (Characteristics of a waiting-line system, moderate)
question

14. In the analysis of queuing models, the Poisson distribution often describes arrival rates and service times are often described by the negative exponential distribution.

True (Characteristics of a waiting-line system, moderate)
question

15. The study of waiting lines calculates the cost of providing good service but does not value the cost of customers’ waiting time.

False (Queuing costs, moderate)
question

16. As the average service rate grows larger, the slope of the distribution of service time probabilities grows larger and larger, eventually becoming positive.

False (The variety of queuing models, easy)
question

17. Four of the most widely used waiting line models—M/M/1 or A, M/M/S or B, M/D/1 or C, and Limited population or D—all share three characteristics: Poisson arrivals, FIFO discipline, and exponential service times.

False (The variety of queuing models, moderate)
question

18. In the M/M/1 waiting line model with an arrival rate of 2 per hour and a service rate of 6 per hour, the utilization factor for the system is approximately 0.333.

True (The variety of queuing models, easy)
question

19. The greater the margin by which the arrival rate exceeds the service rate, the better the performance of the waiting line.

False (The variety of queuing models, easy)
question

20. An M/M/1 model and an M/D/1 model each have an arrival rate of 1 per minute and a service rate of 3 per minute; the average queue length of the M/M/1 will be twice that of the M/D/1.

True (The variety of queuing models, moderate)
question

21. A finite population waiting line model has an average service time T of 100 minutes and an average time between service requirements U of 400 minutes; the service factor X is 0.25.

False (The variety of queuing models, moderate)
question

22. Study of waiting-line models helps operations managers better understand a. service systems such as bank teller stations b. maintenance activities that might repair broken machinery c. shop-floor control activities d. service systems such as amusement park rides e. all of the above

e. all of the above
question

23. Which of the following is not a common queuing situation? a. grocery shoppers being served by checkout clerks b. commuters slowing or stopping at toll plazas to pay highway tolls c. machinery waiting to be repaired or maintained d. parcel delivery truck following its computer-generated route e. patients in a health clinic waiting to see one of several doctors

d. parcel delivery truck following its computer-generated route
question

24. In queuing problems, which of the following probability distributions is typically used to describe the number of arrivals per unit of time? a. binomial b. normal c. Poisson d. exponential e. lognormal

c. Poisson
question

25. In queuing problems, which of the following probability distributions is typically used to describe the time to perform the service? a. binomial b. normal c. Poisson d. negative exponential e. lognormal

d. negative exponential
question

26. The common measures of a queuing system’s performance include a. probability that the service facility will be idle, average queue length, probability that the waiting time will exceed a specified duration b. average time each customer spends in the system, probability that the service system will be idle, average time each customer spends in the queue c. average queue length, maximum time a customer may spend in the queue, the utilization factor for the system d. average time each customer spends in the system, maximum queue length, probability of a specific number of customers in the system e. none of the above

b. average time each customer spends in the system, probability that the service system will be idle, average time each customer spends in the queue
question

27. The shopper who says to himself, “I’ve waited too long in this line. I don’t really need to buy this product today,” and leaves the store is an illustration of which element of arrival behavior? a. random arrival b. renege c. random departure d. balk e. none of the above

b. renege
question

28. A waiting line, or queuing, system has three parts, which are a. distribution of arrival times, discipline while waiting, and distribution of service times b. arrival rate, service rate, and utilization rate c. arrival discipline, queue discipline, and service sequencing d. arrival or inputs, queue discipline or the waiting line itself, and the service facility e. sequencing policy, penalty for reneging, and expediting of arrivals

d. arrival or inputs, queue discipline or the waiting line itself, and the service facility
question

29. The source population is considered to be either ________ in its size. a. finite or infinite b. fixed or variable c. known or unknown d. random or scheduled e. small or large

a. finite or infinite
question

30. The potential restaurant customer who says to her husband, “The line looks too long; let’s eat somewhere else,” is an illustration of which element of queue discipline? a. first-in, first-out b. balk c. renege d. random departure e. none of the above

b. balk
question

31. An airline ticket counter, with several agents for one line of customers, is an example of a a. single channel, single phase system b. single channel, multi-phase system c. multi-channel, single phase system d. multi-channel, multi-phase system e. none of the above

c. multi-channel, single phase system
question

32. A concert hall, employing both ticket takers and ushers to seat patrons, behaves typically as a a. multi-channel, single phase system b. multi-channel, multi-phase system c. single channel, single phase system d. single channel, multi-phase system e. none of the above

b. multi-channel, multi-phase system
question

33. If the food service for the university operates a cafeteria with a single serving line, that system behaves most like a a. single channel, single phase system b. single channel, multi-phase system c. multi-channel, single phase system d. multi-channel, multi-phase system e. none of the above

b. single channel, multi-phase system
question

34. The sign at the bank that reads “Wait here for the first available teller” suggests the use of a _____waiting line system. a. single phase b. multi-phase c. single channel d. multi-channel e. multiple line

d. multi-channel
question

35. A small hair styling salon has several operators. While customers do not have appointments, each is waiting to be served by a specific operator. This scenario provides an example of a a. multiple-channel, multi-phase, limited queue length b. single-channel, multi-phase, limited queue length c. multi-channel, limited queue length d. multiple single-channel systems, limited queue length e. none of the above

d. multiple single-channel systems, limited queue length
question

36. A large discount store and supermarket has a hair styling salon on its premises. The salon has several operators. Salon customers can shop in other parts of the store until their name is called for salon service, at which time the customer will be served by the next available stylist. This scenario provides an example of a a. multiple-channel, multi-phase, unlimited queue length b. single-channel, multi-phase, limited queue length c. multi-channel, unlimited queue length d. multiple single-channel systems, limited queue length e. none of the above

c. multi-channel, unlimited queue length
question

37. A university has only one technician in the repair station to care for the computers in the student labs. This system is most likely a. a single channel, limited queue system b. a single channel, limited population system c. a multi-channel, limited queue system d. a multi-channel, limited population system e. none of the above

b. a single channel, limited population system
question

38. “Women and children first!” declares the captain of a sinking ship. His directive employs which of the following queue disciplines in disembarking passengers? a. priority b. random c. FIFO or FIFS d. LIFO or LIFS e. none of the above

a. priority
question

39. A university has several technicians in the repair station to care for the computers in the student labs. This system is most likely a. single channel, limited queue system b. single channel, limited population system c. multi-channel, limited queue system d. multi-channel, limited population system e. none of the above

d. multi-channel, limited population system
question

40. A system in which the customer receives service from only one station and then exits the system is a. a single-phase system b. a single channel system c. a multiple-channel system d. a multiple-phase system e. none of the above

a. a single-phase system
question

41. In a repetitive focus factory, the number of phases found in the system might refer to a. the number of successive operations that have to be performed on a part b. the number of machines doing the same necessary operations c. the number of parts waiting to be processed d. all of the above depending on the layout e. none of the above

a. the number of successive operations that have to be performed on a part
question

42. Which of the following is a measure of queue performance? a. utilization factor b. average queue length c. probability of a specific number of customers in the system d. average waiting time in the line e. all of the above

e. all of the above
question

43. Which of the following is most likely to be served in a last-in, first-served (LIFS) queue discipline? a. customers checking out at a grocery store b. the in-basket on a manager’s desk c. patients entering a hospital emergency room d. patrons waiting to be seated in a casual-dining restaurant e. all of the above

b. the in-basket on a manager’s desk
question

44. In a repetitive focus factory, the number of channels available for the processing of a certain part would likely refer to a. the number of successive operations that have to be performed on that part b. the number of machines doing the same necessary operations c. the number of parts waiting to be processed d. all of the above depending on the layout e. none of the above

b. the number of machines doing the same necessary operations
question

45. A waiting line meeting the assumptions of M/M/1 has average time between arrivals of 20 minutes and services items in an average of 10 minutes each; the utilization factor is approximately a. 0.25 b. 0.33 c. 0.50 d. 0.67 e. 3.00

c. 0.50
question

46. A waiting line model meeting the assumptions of M/M/1 has an arrival rate of 2 per hour and a service rate of 6 per hour; the utilization factor for the system is approximately a. 0.25 b. 0.33 c. 0.50 d. 0.67 e. 3.00

b. 0.33
question

47. As the average service rate increases, the shape of the negative exponential distribution of service times a. grows steadily steeper without limit b. has an ever steeper slope that eventually turns positive c. becomes less gently curved as it moves ever closer to the graph origin d. takes on a more uniform slope over a wide range of service times e. changes in appearance from convex to concave

c. becomes less gently curved as it moves ever closer to the graph origin
question

48. Which one of the following is not a characteristic of a Model A or M/M/1 system? a. exponential service time pattern b. single number of channels c. single number of phases d. Poisson arrival rate pattern e. limited population size

e. limited population size
question

49. Which one of the following is not a characteristic of a Model B or M/M/S system? a. unlimited population size b. single channel c. single queue d. single phase e. Poisson arrival rate pattern

b. single channel
question

50. Which one of the following is not a characteristic of a Model C or M/D/1 system? a. single channel b. single phase c. Poisson arrival rate pattern d. exponential service time pattern e. unlimited population size

d. exponential service time pattern
question

51. In the basic queuing model (M/M/1), service times are described by a. continuous probability distributions b. negative exponential probability distributions c. Poisson probability distributions d. normal probability distributions e. lognormal distributions

b. negative exponential probability distributions
question

52. In the basic queuing model (M/M/1), arrival rates are distributed by a. continuous probability distributions b. normal probability distributions c. negative exponential probability distributions d. Poisson distributions e. lognormal distributions

d. Poisson distributions
question

53. A single-phase waiting-line system meets the assumptions of constant service time or M/D/1. Units arrive at this system every 10 minutes on average. Service takes a constant 4 minutes. The average length of the queue Lq is a. 0.4 b. 0.133 c. 4.167 d. 4.583 e. 6

b. 0.133
question

54. Which of the following is not an assumption of the M/M/1 model? a. The first customers to arrive are the first customers served. b. Each arrival comes independently of the arrival immediately before and after that arrival. c. The population from which the arrivals come is very large or infinite in size. d. Customers do not renege. e. Service times occur according to a normal curve.

e. Service times occur according to a normal curve.
question

55. A single-phase waiting-line system meets the assumptions of constant service time or M/D/1. Units arrive at this system every 12 minutes on average. Service takes a constant 8 minutes. The average length of the queue Lq is approximately a. 0.67 b. 2.5 c. 4.5 d. 5.0 e. 7.5

a. 0.67
question

56. A single-phase waiting-line system meets the assumptions of constant service time or M/D/1. Units arrive at this system every 12 minutes on average. Service takes a constant 8 minutes. The average number in the system Ls is approximately a. 2.25 b. 2.5 c. 3.0 d. 1.33 e. 5.0/

d. 1.33
question

57. A queuing model which follows the M/M/1 assumptions has = 2 and = 3. The average number in the system is a. 2/3 b. 1 c. 1.5 d. 2 e. 6

d. 2
question

58. A queuing model which follows the M/M/1 assumptions has = 3 and = 2. The average number in the system is a. -3 b. 3 c. 0.667 d. 150 percent e. growing without limit, since is larger than .

e. growing without limit, since is larger than .
question

59. Students arrive randomly at the help desk of the computer lab. There is only one service agent, and the time required for inquiry varies from student to student. Arrival rates have been found to follow the Poisson distribution, and the service times follow the negative exponential distribution. The average arrival rate is 12 students per hour, and the average service rate is 20 students per hour. What is the average service time for this problem? a. 1 minute b. 2 minutes c. 3 minutes d. 5 minutes e. 20 minutes

c. 3 minutes
question

60. A queuing model which follows the M/M/1 assumptions has = 10 and = 12. The average number in the system is a. 0.83 b. 2 c. 2.5 d. 5 e. 6

d. 5
question

61. A queuing model which follows the M/M/1 assumptions has = 2 and = 8. The average number in the system Ls is ______ and the utilization of the system is _______. a. 3; 100 percent b. 0.33; 25 percent c. 4; 33 percent d. 6; 25 percent e. 4; 25 percent

b. 0.33; 25 percent
question

62. Four of the most widely used waiting line models—M/M/1 or A, M/M/S or B, M/D/1 or C, and Limited population or D—all share three characteristics, which are a. normal arrivals, FIFO discipline, and normal service times b. Poisson arrivals, FIFO discipline, and a single-service phase c. Poisson arrivals, FIFO discipline, and exponential service times d. Poisson arrivals, no queue discipline, and exponential service times e. none of these

b. Poisson arrivals, FIFO discipline, and a single-service phase
question

63. A queuing model which follows the M/M/1 assumptions has = 2 and = 3. The average waiting time in the system is a. 2/3 b. 1 c. 1.5 d. 2 e. 6

b. 1
question

64. Students arrive randomly at the help desk of the computer lab. There is only one service agent, and the time required for inquiry varies from student to student. Arrival rates have been found to follow the Poisson distribution, and the service times follow the negative exponential distribution. The average arrival rate is 12 students per hour, and the average service rate is 20 students per hour. What is the utilization factor? a. 20% b. 30% c. 40% d. 50% e. 60%

e. 60%
question

65. A finite population waiting line model has an average service time T of 100 minutes and an average time between service requirements U of 400 minutes; the service factor X is a. 0.20 b. 0.25 c. 4 d. 5 e. 300 minutes

a. 0.20
question

66. A finite population waiting line model has an average service time T of 200 minutes and an average time between service requirements U of 300 minutes; the service factor X is a. 0.20 b. 0.40 c. 0.60 d. 0.67 e. 2.5

b. 0.40
question

67. Students arrive randomly at the help desk of the computer lab. There is only one service agent, and the time required for inquiry varies from student to student. Arrival rates have been found to follow the Poisson distribution, and the service times follow the negative exponential distribution. The average arrival rate is 12 students per hour, and the average service rate is 20 students per hour. A student has just entered the system. How long is she expected to stay in the system? a. 0.125 minute b. 0.9 minute c. 1.5 minutes d. 7.5 minutes e. 0.075 hour

d. 7.5 minutes
question

68. Students arrive randomly at the help desk of the computer lab. There is only one service agent, and the time required for inquiry varies from student to student. Arrival rates have been found to follow the Poisson distribution, and the service times follow the negative exponential distribution. The average arrival rate is 12 students per hour, and the average service rate is 20 students per hour. How many students, on the average, will be waiting in line at any one time? a. 0.9 students b. 1.5 students c. 3 students d. 4 students e. 36 students

a. 0.9 students
question

69. A waiting-line system that meets the assumptions of M/M/S has = 5, = 4, and M = 2. For these values, Po is approximately 0.23077 and Ls is approximately 2.05128. The average time a unit spends waiting in this system a. is approximately 0.1603 b. is approximately 0.2083 c. is approximately 0.4103 d. is approximately 0.8013 e. cannot be calculated because is larger than

a. is approximately 0.1603
question

70. A waiting-line system that meets the assumptions of M/M/1 has = 1, = 4. For this system, Po is ______ and utilization is ________. a. 0.75; 0.25 b. 0.80; .20 c. -3; -4 d. 3; 4 e. none of these

a. 0.75; 0.25
question

71. A waiting-line system that meets the assumptions of M/M/S has = 5, = 4, and M = 2. For these values, Po is approximately 0.23077 and Ls is approximately 2.05128. The average number of units waiting in the queue a. is approximately 0.1603 b. is approximately 0.4103 c. is approximately 0.8013 d. is approximately 1.0417 e. cannot be calculated because is larger than

c. is approximately 0.8013
question

72. A waiting-line system that meets the assumptions of M/M/1 has = 1, = 4. For this system, the probability of more than two units in the system is approximately a. zero b. 0.015625 c. 0.0625 d. 0.25 e. 0.9375