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SW3 Flashcards

1
Q

Most services are characterized by the IHIP properties. What are those ?

A

I – Intangible: Services cannot be touched. Services are experienced!
H – Heterogeneous: customer involvement in delivery process results in variability
I - Instantaneous: Production, distribution and consumption happen at the same
time
P – Perishable: services cannot be stored

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2
Q

What are “Short- to medium-term capacity management strategies”?

A

Level capacity:
* In this case scarce or
expensive resources
are maintained at a
constant level, and the
organisation must
manage the
consequential issues
for customer
satisfaction and
operational service
quality.
Chase capacity:
* The service
organisation attempts
to match supply to
demand as much as
possible by building
flexibility into the
operation. The prime
objective is to provide
high levels of service
availability or fast
response, in the most
efficient manner.
Demand management:
* Rather than change
the capacity of the
service operation, the
organisation
influences the demand
profile to ‘smooth’ the
load on the resources.

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3
Q

What is “Level capacity” as a capacity management strategy?

A
  • In this case scarce or
    expensive resources
    are maintained at a
    constant level, and the
    organisation must
    manage the
    consequential issues
    for customer
    satisfaction and
    operational service
    quality.
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4
Q

What is “Chase capacity” as a capacity management strategy?

A
  • The service
    organisation attempts
    to match supply to
    demand as much as
    possible by building
    flexibility into the
    operation. The prime
    objective is to provide
    high levels of service
    availability or fast
    response, in the most
    efficient manner.
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5
Q

What is “Demand management” as a capacity management strategy?

A

Rather than change
the capacity of the
service operation, the
organisation
influences the demand
profile to ‘smooth’ the
load on the resources.

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6
Q

Waiting queues: What type of “Queue designs” are there?

A

(a) Multiple lines, multiple servers and
(b)Single line, multiple servers

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7
Q

Queue parameters: how are queues described?

A

Notation: a/b/c
a Probability distribution of the arrival rate
D = Deterministic
M = Poisson
G = General
b Probability distribution of service time
D = Deterministic
M = Exponential
G = General
c Number of servers

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8
Q

Queue parameters: What does a mean?

A

Probability distribution of the arrival rate

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9
Q

Queue parameters: What dies b mean?

A

Probability distribution of service time

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10
Q

Queue parameters: What does c mean?

A

Number of servers

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11
Q

Queue parameters: What does D mean in the context of a ?

A

Deterministic

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12
Q

Queue parameters: What does M mean in the context of a?

A

Poisson

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13
Q

Queue parameters: What does G mean in the context of a?

A

General

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14
Q

Queue parameters: What does D mean in the context of b?

A

Deterministic

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15
Q

Queue parameters: What does M mean in the context of b?

A

Exponential

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16
Q

Queue parameters: What does G mean in the context of b?

A

General

17
Q

QUEUE CHARACTERISTICS: What does: M/M/1 mean?

A

 Poisson-distributed arrivals often realistic
 Exponentially distributed handling times often out of touch with reality
 Very nice analytical properties: E.g. distribution of output is Poisson
 Very simple formulas for key performance indicators

18
Q

QUEUE CHARACTERISTICS: What does: M/M/c mean?

A

 Like M/M/1 with more than one server
 Formulas for key performance indicators more complex than for M/M/1

19
Q

QUEUE CHARACTERISTICS: What does: M/G/1 mean?

A

 Often more realistic than M/M/1, since distribution of handling times arbitrarily
 Distribution of output not Poisson
 Simple formulas available for some KPIs

20
Q

QUEUE CHARACTERISTICS: What does: G/G/c mean?

A

 Very realistic modeling possible
 Calculation of performance, if possible, very complex

21
Q

M/M/1 QUEUES: What does Pn mean?

A

Probability that there are n customers in the system at any given time

22
Q

M/M/1 QUEUES: What does LQ mean?

A

(Length Queue) Expected number of customers in the queue

23
Q

M/M/1 QUEUES: What does WQ mean?

A

(Waiting time Queue) Expected time of a customer in the queue

24
Q

M/M/1 QUEUES: What does LS mean?

A

(Length System) Expected number of customers in the system

25
Q

M/M/1 QUEUES: What does WS mean?

A

(Waiting time System) Expected time of a customer in the system

26
Q

M/M/1 QUEUES: What does A mean?

A

Average interarrival time

27
Q

M/M/1 QUEUES: What does S mean?

A

Average service time

28
Q

M/M/1 QUEUES: What does ρ mean?

A

Utilization factor (ρ < 1)

29
Q

M/M/1 QUEUES: What does n mean?

A

Number of customers in the system (queue plus service)

30
Q

Excercise: Situation  A single postal employee in a single post office serves all
customers
 The customer arrivals are poisson distributed with arrival rate
λ
= 22 customers
/hour
 The postal worker can serve customers with a rate of
µ = 30
customers
/hour
(service rate). The service rate is expontentially
distributed
.
Questions
1. To what extent of his time is the postal employee busy serving
customers?
2. What is the probability that the post office is empty?
3. What is the probability that exactly two customers will be in
the post office?
4. What is the probability that there will be three or fewer
customers in the post office?
5. What is the probability that there will be two or more
customers in the post office?
6. What is the expected number of customers who are
in the post office?
7. What is the expected number of customers served by
the postal officer?
8. What is the expected number of customers in the
queue?
9. How long does a customer have to wait on average
to be served? And how long does he stay in the post
office on average?

A
  1. To what extent of his time is the postal employee busy serving customers?
    ρ= 22/30 = 73.3%
  2. What is the probability that the post office is empty?
    P0 = 1-ρ =26,7%
  3. What is the probability that exactly two customers will be in the post office?
    𝑃2 = 𝜌^2(1 − 𝜌) =(22/30)^2 (1-22/30) = 14.3%
  4. What is the probability that there will be three or fewer customers in the post office?
    𝑃0+ 𝑃1 + 𝑃2 + 𝑃3= (𝜌0 + 𝜌1 + 𝜌2 + 𝜌3)(1 − 𝜌)=
    (1+.733 + .533 + .394)    .267 = 71%
  5. What is the probability that there will be two or more customers in the post office?
    1 − 𝑃0 − 𝑃1 = 1 − .267 - .196 = .537
  6. What is the expected number of customers who are in the post office?
    LS = ρ/(1-ρ) = 0,733/(1-0.733) = 2.75
  7. . What is the expected number of customers served by the postal officer?
    ρ = 0.733
  8. What is the expected number of customers in the queue?
    LQ = ρ^2/(1-ρ) = 0.733^2/1-0.733 = 2.02
    oder LQ = LS - ρ = 2.75 -0.733 =2.02
  9. WQ = ρ^2/ λ (1-ρ) => WQ = 2.02 Aufträge/22 Aufträge pro Stunde = 5.5 Minuten
    WS = ρ / λ(1-ρ) => WS = 2.75 Aufträge / 22 Aufträge pro Stunde = 7.5 Minuten

DPS (5 decks)

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