Service Processes

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• Service Processes

MAN-4504
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Learning Objectives

• Understand the characteristics of service
  processes and how they are different from
  manufacturing processes
• Be able to classify service processes
• Understand waiting line (queuing) analysis
• Be able to model some common waiting line
  situations and estimate server utilization, the
  length of the waiting line, and average customer
  wait time

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Service Businesses
A service business is the management of
organizations whose primary business requires
interaction with the customer to produce the
service

• Generally classified according to who the
  customer is
• Financial services
• Health care
• A contrast to manufacturing

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Service-System Design Matrix
Degree of customer/server contact
Buffered
Permeable
Reactive
High
core (none)
system (some)
system (much)
Low
Face-to-face total customization
Face-to-face loose specs
Sales Opportunity
Production Efficiency
Face-to-face tight specs
Phone Contact
Internet on-site technology
Mail contact
High
Low
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Components of the Queuing System
Queue or
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Customer Service Population Sources
Population Source
Example Number of machines needing repair when a
company only has three machines.
Example The number of people who could wait in a
line for gasoline.
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Service Pattern
Service Pattern
Example Items coming down an automated assembly
line.
Example People spending time shopping.
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The Queuing System
Queuing System
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Examples of Line Structures
Single Phase
Multiphase
Single Channel
Multichannel
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Degree of Patience
No Way!
No Way!
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Waiting Line Models
Source
Model
Layout
Population
Service Pattern
1
Single channel
Infinite
Exponential
2
Single channel
Infinite
Constant
3
Multichannel
Infinite
Exponential
These three models share the following
characteristics

• Single phase
• Poisson arrival
• FCFS
• Unlimited queue length

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Notation Infinite Queuing Models 1-3
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Infinite Queuing Models 1-3 (Continued)
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Example Model 1
At a fast food drive-up window customers arrive
at the rate of 25 per hour, and can be served in
an average of two minutes.
Determine A) Average utilization of the
window? B) Average number of customers in
line? C) Average number of customers in the
system? D) Average waiting time in line? E)
Average waiting time in the system? F)
Probability that exactly two cars will be in the
system?
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Example Model 1
A) Average utilization of the window?
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Example Model 1
B) Average number of customers in line?
C) Average number of customers in the system?
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Example Model 1
D) Average waiting time in line?
E) Average waiting time in the system?
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Example Model 1
F) Probability of exactly two cars in the system
(one being served and the other waiting in line)?
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Example Model 2
An automated pizza vending machine heats and
dispenses a slice of pizza in 4
minutes. Customers arrive at a rate of one every
6 minutes with the arrival rate exhibiting a
Poisson distribution.
Determine A) The average number of customers
in line. B) The average total waiting time in
the system.
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Example Model 2
A) Average number of customers in line.
B) Average total waiting time in the system.
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Example Model 3
Recall the Model 1 example At a fast food
drive-up window customers arrive at the rate of
25 per hour, and can be served in an average of
two minutes.
If an identical window (and an identically
trained server) were added, what would the
effects be on the average number of cars in the
system and the total time customers wait before
being served?
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Example Model 3
Average number of cars in the system
Total time customers wait before being served
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But there is an easier way

• For these simple models, use Excel template (see
  link in lecture notes)
• For more complicated models, use specialized
  software (like SIMSCRIPT II.5)

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Question Bowl

• Which of the following is an example of a
  Service Business?
• Law firm
• Hospital
• Bank
• Retail store
• All of the above

Answer e. All of the above
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Question Bowl

• Based on the Service-System Design Matrix,
  which of the following has a lower level of
  production efficiency?
• Face-to-face loose specs
• Phone contact
• Internet and on-site technology
• Face-to-face tight specs
• Mail contact

Answer a. Face-to-face loose specs
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Question Bowl

• The central problem for virtually all queuing
  problems is which of the following?
• Balancing labor costs and equipment costs
• Balancing costs of providing service with the
  costs of waiting
• Minimizing all service costs in the use of
  equipment
• All of the above
• None of the above

Answer b. Balancing costs of providing service
with the costs of waiting
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Question Bowl

• Customer Arrival populations in a queuing
  system can be characterized by which of the
  following?
• Poisson
• Infinite
• Patient
• FCFS
• None of the above

Answer b. Infinite
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Question Bowl

• Customer Arrival rates in a queuing system can
  be characterized by which of the following?
• Constant
• Infinite
• Finite
• All of the above
• None of the above

Answer a. Constant
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Question Bowl

• An example of a queue discipline in a queuing
  system is which of the following?
• Single channel, multiphase
• Single channel, single phase
• Multichannel, single phase
• Multichannel, multiphase
• None of the above

Answer e. None of the above (These are the rules
for determining the order of service to
customers, which include FCFS, reservation
first, highest-profit customer first, etc.)
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Question Bowl

• Withdrawing funds from an automated teller
  machine is an example in a queuing system of
  which of the following line structures?
• Single channel, multiphase
• Single channel, single phase
• Multichannel, single phase
• Multichannel, multiphase
• None of the above

Answer b. Single channel, single phase
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Question Bowl

• Refer to Model 1 in the textbook. If the service
  rate is 15 per hour, what is the average service
  time for this queuing situation?
• 16.00 minutes
• 0.6667 hours
• 0.0667 hours
• 16 of an hour
• Can not be computed from data above

Answer c. 0.0667 hours (1/150.0667)
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Question Bowl

• Refer to Model 1 in the textbook. If the arrival
  rate is 15 per hour, what is the average time
  between arrivals for this queuing situation?
• 16.00 minutes
• 0.6667 hours
• 0.0667 hours
• 16 of an hour
• Can not be computed from data above

Answer c. 0.0667 hours (1/150.0667)