Question 1

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

Accepted Answer

A) True 
 B)False

Question 2

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

Accepted Answer

A) True 
 B)False

Question 3

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

Accepted Answer

A) True 
 B)False

Question 4

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

Accepted Answer

A) True 
 B)False

Question 5

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 mach

Question 6

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 probability distribution. 
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 probability distribution.

Question 7

A waiting line meeting the M/M/1 assumptions has an arrival rate of 10 per hour and a service rate of 12 per hour.What is the probability that the waiting line is empty?

Accepted Answer

P_o = 1 - λ/

Question 8

Little's Law is not applicable in which of the following situations?

Accepted Answer

A) the opening of a toy store on Black Friday morning 
B) a 24-hour supermarket 
C) a gas station with 24-hour self-service pumps 
D) B and C 
E) It is applicable to A,B,and C. 
A) the opening of a toy store on Black Friday morning 
B) a 24-hour supermarket 
C) a gas station with 24-hour self-service pumps 
D) B and C 
E) It is applicable to A,B,and C.

Question 9

A waiting-line system that meets the assumptions of M/M/S has λ = 5,μ = 4,and M = 2.For these values,Po is approximately 0.23077,and Ls is approximately 2.05128.What is the average number of units waiting in the queue?

Accepted Answer

A) approximately 0.1603 
B) approximately 0.4103 
C) approximately 0.8013 
D) approximately 1.0417 
E) Cannot be calculated because λ is larger than μ. 
A) approximately 0.1603 
B) approximately 0.4103 
C) approximately 0.8013 
D) approximately 1.0417 
E) Cannot be calculated because λ is larger than μ.

Question 10

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.On average,how long does it take to service each student?

Accepted Answer

A) 1 minute 
B) 2 minutes 
C) 3 minutes 
D) 5 minutes 
E) 20 minutes 
A) 1 minute 
B) 2 minutes 
C) 3 minutes 
D) 5 minutes 
E) 20 minutes

Question 11

Suppose that a fast food restaurant wants the average line to be 4 customers and that 80 customers arrive each hour.How many minutes will the average customer be forced to wait in line?

Accepted Answer

Little's Law: 4 customers = (8

Question 12

The source population is considered to be either ________ in its size.

Accepted Answer

A) finite or infinite 
B) fixed or variable 
C) known or unknown 
D) random or scheduled 
E) small or large 
A) finite or infinite 
B) fixed or variable 
C) known or unknown 
D) random or scheduled 
E) small or large

Question 13

Which one of the following is NOT a characteristic of a Model A or M/M/1 system?

Accepted Answer

A) exponential service time pattern 
B) single number of servers 
C) single number of phases 
D) Poisson arrival rate pattern 
E) limited population size 
A) exponential service time pattern 
B) single number of servers 
C) single number of phases 
D) Poisson arrival rate pattern 
E) limited population size

Question 14

At the order fulfillment center 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 = 1

Question 15

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

Accepted Answer

A) True 
 B)False

Question 16

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.What is the average length of the queue Lq in units?

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 17

A crew of mechanics at the Highway Department Garage repair vehicles that break down at an average of λ = 8 vehicles per day (approximately Poisson in nature).The mechanic crew can service an average of μ= 11 vehicles per day with a repair time distribution that approximates an exponential distribution.The crew cost is approximately $300 per day.The cost associated with lost productivity from the breakdown is estimated at $150 per vehicle per day (or any fraction thereof).Which is cheaper,the existing system with one service crew,or a revised system with two service crews?

Accepted Answer

L_s for the single server is 8 / (11 - 8)=

Question 18

What does it mean to have a patient customer in a waiting line?

Accepted Answer

A patient customer is one who

Question 19

The sign at the bank that reads,"Wait here for the first available teller," suggests the use of a ________ waiting line system.

Accepted Answer

A) dynamic-server,single-phase 
B) random-server,single-phase 
C) single-server,multiphase 
D) multiple-server,single-phase 
E) multiple-server,multiphase 
A) dynamic-server,single-phase 
B) random-server,single-phase 
C) single-server,multiphase 
D) multiple-server,single-phase 
E) multiple-server,multiphase

Question 20

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?

Accepted Answer

A) 0.125 minutes 
B) 0.9 minutes 
C) 1.5 minutes 
D) 7.5 minutes 
E) 0.075 hours 
A) 0.125 minutes 
B) 0.9 minutes 
C) 1.5 minutes 
D) 7.5 minutes 
E) 0.075 hours

Exam 25: Waiting-Line Models

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

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

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

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

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?

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

A waiting line meeting the M/M/1 assumptions has an arrival rate of 10 per hour and a service rate of 12 per hour.What is the probability that the waiting line is empty?

Little's Law is not applicable in which of the following situations?

A waiting-line system that meets the assumptions of M/M/S has λ = 5,μ = 4,and M = 2.For these values,Po is approximately 0.23077,and Ls is approximately 2.05128.What is the average number of units waiting in the queue?

Suppose that a fast food restaurant wants the average line to be 4 customers and that 80 customers arrive each hour.How many minutes will the average customer be forced to wait in line?

The source population is considered to be either ________ in its size.

Which one of the following is NOT a characteristic of a Model A or M/M/1 system?

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

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.What is the average length of the queue Lq in units?

What does it mean to have a patient customer in a waiting line?

The sign at the bank that reads,"Wait here for the first available teller," suggests the use of a ________ waiting line system.

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A waiting-line system that meets the assumptions of M/M/S has λ = 5,μ = 4,and M = 2.For these values,P_o is approximately 0.23077,and L_s is approximately 2.05128.What is the average number of units waiting in the queue?

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.What is the average length of the queue L_q in units?