Question 1

As the average service rate μ increases, the shape of the negative exponential distribution of service times

Accepted Answer

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. 
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.

Question 2

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

Accepted Answer

A)  0.67. 
B)  2.5. 
C)  4.5. 
D)  5.0. 
E)  7.5. 
A)  0.67. 
B)  2.5. 
C)  4.5. 
D)  5.0. 
E)  7.5.

Question 3

Which of the following represents a customer that reneged due to the waiting-line?

Accepted Answer

A)  A husband and wife decide to eat out instead after seeing the movie ticket line. 
B)  A car drives past the first fast-food restaurant on Hamburger Row because the drive-through was full. 
C)  A Black Friday shopper skipped one store because the line went around the building. 
D)  A student ordered pizza online because the phone line was busy. 
E)  A customer at a gas station went inside to buy a soda, but after waiting in line for a minute left the soda behind and went outside empty-handed. 
A)  A husband and wife decide to eat out instead after seeing the movie ticket line. 
B)  A car drives past the first fast-food restaurant on Hamburger Row because the drive-through was full. 
C)  A Black Friday shopper skipped one store because the line went around the building. 
D)  A student ordered pizza online because the phone line was busy. 
E)  A customer at a gas station went inside to buy a soda, but after waiting in line for a minute left the soda behind and went outside empty-handed.

Question 4

What are the assumptions underlying the M/M/1 waiting line model? Which of these also hold for the M/D/1 model?

Accepted Answer

The assumptions underlying the standard

Question 5

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.

Accepted Answer

A) True 
 B)False

Question 6

Which of the following is a requirement for application of Little's Law to be valid?

Accepted Answer

A)  arrival rates that follow the Poisson distribution 
B)  FIFO queue discipline 
C)  steady state conditions 
D)  single channel 
E)  multiple phase 
A)  arrival rates that follow the Poisson distribution 
B)  FIFO queue discipline 
C)  steady state conditions 
D)  single channel 
E)  multiple phase

Question 7

Arrivals or inputs to a waiting-line system have characteristics that include

Accepted Answer

A)  population size. 
B)  population behaviour. 
C)  population's statistical distribution. 
D)  population size and population's statistical distribution. 
E)  population size, population behaviour and population's statistical distribution. 
A)  population size. 
B)  population behaviour. 
C)  population's statistical distribution. 
D)  population size and population's statistical distribution. 
E)  population size, population behaviour and population's statistical distribution.

Question 8

Describe the important operating characteristics of a queuing system.

Accepted Answer

The operating characteristics usually co

Question 9

A queuing model which follows the M/M/1 assumptions has λ = 3 and μ = 2. The average number in the system is

Accepted Answer

A)  -3. 
B)  3. 
C)  0.667. 
D)  150%. 
E)  growing without limit, since λ is larger than μ. 
A)  -3. 
B)  3. 
C)  0.667. 
D)  150%. 
E)  growing without limit, since λ is larger than μ.

Question 10

A finite population waiting line model with a single server has an average service time T of 50 minutes and an average time between service requirements U of 350 minutes. Calculate the service factor X. If the population consists of 5 elements, what are the average number waiting, the average number being serviced, and the average number running? Refer to Table D.8 in the text.

Accepted Answer

The service factor is X = T / (T + U) =

Question 11

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.

Accepted Answer

A) True 
 B)False

Question 12

Which of the following is not an assumption of the M/M/1 model?

Accepted Answer

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. 
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.

Question 13

What costs are present in waiting line analysis? How do these costs vary with the level of service?

Accepted Answer

The costs are the cost of providing serv

Question 14

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?

Accepted Answer

A)  20% 
B)  30% 
C)  40% 
D)  50% 
E)  60% 
A)  20% 
B)  30% 
C)  40% 
D)  50% 
E)  60%

Question 15

A waiting-line system that meets the assumptions of M/M/1 has λ = 1, μ = 4. For this system, Po is ________ and utilization is ________.

Accepted Answer

A)  0.75; 0.25 
B)  0.80; .20 
C)  -3; -4 
D)  3; 4 
E)  none of these 
A)  0.75; 0.25 
B)  0.80; .20 
C)  -3; -4 
D)  3; 4 
E)  none of these

Question 16

A manufacturing plant is trying to determine how long the average line for a repair process will be. If 10 machines arrive each hour and must wait 6 minutes in the line, how long will the line be, on average?

Accepted Answer

Little's Law X machines = 10 m

Question 17

Suppose that a service facility has an average line of 2 customers that must wait, on average, 5 minutes for service. How many customers are arriving per hour?

Accepted Answer

Use Little's Law that 2 custom

Question 18

A manufacturing plant is trying to determine how long the average line for a repair process will be. If 10 machines arrive each hour and must wait 7 minutes in the line, how long will the line be, on average?

Accepted Answer

Little's Law X machines = 10 m

Question 19

Study of waiting-line models helps operations managers better understand

Accepted Answer

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. 
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.

Question 20

At the order fulfillment centre of a major mail-order firm, customer orders, already packaged for shipment, arrive at the sorting machine to be sorted for loading onto the appropriate truck for the parcel's address. The arrival rate at the sorting machine is at the rate of 140 per hour following a Poisson distribution. The machine sorts at the constant rate of 150 per hour.
a. What is the utilization rate of the system?
b. What is the average number of packages waiting to be sorted?
c. What is the average number of packages in the sorting system?
d. How long must the average package wait until it gets sorted?

Accepted Answer

(a) The utilization rate is = 140/150 =

Exam 21: Waiting-Line Models

As the average service rate μ increases, the shape of the negative exponential distribution of service times

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

Which of the following represents a customer that reneged due to the waiting-line?

What are the assumptions underlying the M/M/1 waiting line model? Which of these also hold for the M/D/1 model?

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.

Which of the following is a requirement for application of Little's Law to be valid?

Arrivals or inputs to a waiting-line system have characteristics that include

Describe the important operating characteristics of a queuing system.

A queuing model which follows the M/M/1 assumptions has λ = 3 and μ = 2. The average number in the system is

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.

Which of the following is not an assumption of the M/M/1 model?

What costs are present in waiting line analysis? How do these costs vary with the level of service?

A waiting-line system that meets the assumptions of M/M/1 has λ = 1, μ = 4. For this system, Po is ________ and utilization is ________.

A manufacturing plant is trying to determine how long the average line for a repair process will be. If 10 machines arrive each hour and must wait 6 minutes in the line, how long will the line be, on average?

Suppose that a service facility has an average line of 2 customers that must wait, on average, 5 minutes for service. How many customers are arriving per hour?

A manufacturing plant is trying to determine how long the average line for a repair process will be. If 10 machines arrive each hour and must wait 7 minutes in the line, how long will the line be, on average?

Study of waiting-line models helps operations managers better understand

Operations and Productivity

Operations Strategy in a Global Environment

Project Management

Forecasting

Design of Goods and Services

Managing Quality

Process Strategy and Sustainability

Location Strategies

Layout Strategies

Human Resources, Job Design, and Work Measurement

Supply-Chain Management

Inventory Management

Aggregate Planning

Material Requirements Planning Mrp and Erp

Short-Term Scheduling

Lean Operations

Maintenance and Reliability

Decision-Making Tools

Linear Programming

Transportation Models

Learning Curves

Simulation

Supply Chain Management Analytics

Sustainability in the Supply Chain

Statistical Process Control

Capacity and Constraint Management

Filters

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 L_q is approximately

A waiting-line system that meets the assumptions of M/M/1 has λ = 1, μ = 4. For this system, P_o is and utilization is .