Why Is There Waiting?
Waiting lines tend to form even when a system is not fully loaded
Variability
Why waiting lines cause concern:
The cost to provide waiting space
A possible loss of business when customers leave the line before being served or refuse to wait at all
A possible loss of goodwill
A possible reduction in customer satisfaction
The goal of waiting line management is to minimize total costs:
Costs associated with customers waiting for service
Capacity cost
The basic characteristics of waiting lines
Population source
Number of servers (channels)
Arrival and service patterns
Population Source
Infinite source
Finite source
Channels and Phases
A server in a service system
It is assumed that each channel can handle one customer at a time
The number of steps in a queuing system
Arrival pattern VS
Service pattern
Most commonly used models assume the arrival rate can be described by the Poisson distribution
Arrivals per unit of time
Equivalently, interarrival times are assumed to follow the negative exponential distribution
The time between arrivals
Service times a
Queue discipline
Most commonly encountered rule is that service is provided on a first-come, first-served (FCFS) basis
Non FCFS applications do not treat all customer waiting costs as the same
Four basic infinite source models
Single server, exponential service time
Single server, constant service time
Multiple servers, exponential service time
Multiple priority service, exponential service time
In a theme park like Disney world, reservation systems are a win-lose situation since only those holding reservations are satisfied
False
A multiple channel system assumes that each server will have its own waiting line and line changing is not permitted.
false
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.
true
All infinite source queuing models require the system utilization to be less than 1.0.
true
Balking is when customers grow impatient and leave a line.
false
Offering an "early bird" special at a restaurant to reduce waiting times during peak hours is an example of ____________.
demand shifting
Which of the following is not generally considered as a measure of system performance in a queuing analysis?
average serving time
To reduce the average number waiting in line, it is important to increase utilization.
false
The goal of waiting line management is to eliminate customer waiting lines.
false
If variation in arrival and service rates can be reduced, waiting lines will be shortened.
true
Why is there waiting in an infinite source queuing system?
variability in arrival and service rates
If a firm has reached the point at which further reducing waiting time is not economically feasible, reducing the ______________ is sometimes attractive.
perceived waiting time
The total cost curve:
Starts high, declines, then increases again.
The goal of waiting line management is to minimize waiting time.
false
In a _______ system, customers enter the waiting line, receive service and leave.
Queuing
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:
6 per hour
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.
false
Which of the following would reduce perceived waiting times most dramatically in a doctor's office?
having the patient fill out forms
For a system that has a low utilization ratio, decreasing service capacity slightly will have only negligible effect on customer waiting time.
true
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:
.40
A basic difference between infinite source and finite source queuing models is:
size of potential calling population
A ________ is one way of reducing perceived waiting time.
Diversion
In a single-channel system, the utilization is equal to the arrival rate divided by the service rate.
true
In an infinite source model, the average number being served is equal to the ratio of the arrival rate to the service rate.
true
According to Little's Law, the number of people in line depends on the time of day that they arrive.
false
A queuing system has four crews with three members each. The number of "servers" is:
3