chapter 2 - problem formulation

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Simulation and Modelling

2 Problem Formulation

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Lessons

1. Introduction

2. Formal Problem Statement

3. Orientation4. Project Objectives

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1. Introduction

Goal: understanding what is to be

accomplished by performing the study.

The activities:

1. A formal problem statement

2. Orientation of the system

3. Establishment of specific project objectives

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2. Formal Problem Statement

Goal:

Provide both the practitioner and the potential audience

with a clearly understandable high-level justification for

the simulation. The goal including:

1. Increasing customer satisfaction

2. Increasing throughput

3. Reducing waste

4. Reducing work in progress

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Increasing Customer Satisfaction

Increasing customer satisfaction is of fundamental interest inany system involving service operations.

This type of system typically includes waiting or processingqueues.

Reductions in queue time usually result in increased customersatisfaction.

Customer satisfaction may also involve delivering productswhen promised.

Reductions in the number of tardy jobs will reduce operatingcosts associated with the loss of goodwill and will increasecustomer satisfaction.

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Increasing Throughput

Increasing throughput involves the amount ofproducts or number of jobs that can beprocessed over a given period of time.

This can involve the elimination orimprovement of different process operations.

It can also include the identification and

redesign of bottleneck processes.

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Reducing Waste

Reducing waste results in reduced operatingcosts and increased net profits.

Waste can be reduced through reductions in

spoilage and obsolescence. Spoilage can involve processes that are time

and temperature critical.

Obsolescence waste can result from an

organizations inability to bring its product tothe market on time.

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Reducing Work in Progress

Work in progress is work that requires further processing forcompletion.

Work in progress is commonly found in processes that requiremultiple discrete operations.

Work in progress typically requires storage before the nextprocess can be carried out.

Reducing work in progress reduces process costs associatedwith resource capacity and storage requirements.

Large amounts of work in progress can result from insufficient

resource capacity or poor operating policies. Reducing work in progress can decrease the space needed for

manufacturing or distribution facilities.

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Tools for Developing the Problem

Statement

Fishbone/Cause-Effect/Ishikawa Chart The Fishbone chart is also known as the cause-and-effect

diagram, manmachinematerial chart, and as the Isikawachart (Suzaki, 1987).

The purpose of this chart is to identify the cause of theproblem oreffect of interest.

Pareto Chart The Pareto chart is a second technique to help the

practitioner to develop the problem statement.

It may turn out that there are several sources or causes ofthe problem or problems of interest.

This is frequently referred to as the 8020 rule: 80% of theproblem is caused by 20% of the factors.

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Fishbone Chart

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Pareto Chart

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7 Basic Quality Control Tools

1. Histogram

2. Pareto Chart

3. Check Sheet4. Control Chart

5. Flow Chart

6. Fishbone/Cause-Effect/Ishikawa Chart7. Scatter Plot

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Histogram

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Check Sheet

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Control Chart

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Flow Chart

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Scatter Plot

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3. Orientation

Goal: The practitioners familiarizing himself

or herself with the system.

Orientation Process/Types:

1. Initial orientation visit

2. Detailed flow orientation visit

3. Review orientation visit

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Initial Orientation Visit

Goal: To obtain a high-level understanding of the

basic inputs and outputs of the system.

It is important not to attempt to understand too

much detail of the system in the initial visit. After the initial orientation visit, the practitioner

should immediately reflect on the major components

of the process while recollection of the visit is still

fresh.

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Detailed Flow Orientation Visit

Goal: An understanding of how the systemoperates.

The practitioner should make detailed notes on thesystem operation by recording:

1. The types of entities that are processed by the system

2. The number and type of queues

3. The number and type of system resources

4. The sequence of processes as experienced by the entities

5. How the system performance can be measured

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Review Orientation Visit

Goal: To ensure that the understanding of the

system operation is consistent with the

practitioners understanding of the system

and/or flow chart.

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Tools for The Orientation

High degree of access to the system.

Recording devices:

1. Digital camera (pictures, photos)

2. Camcorder (video)

3. Tape recorder, mini recorder (sounds)

4. Computer activity recorder

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4. Project Objectives

Project objectives are dynamic.

Common project objectives may involve

1. Performance-related operating policies

2. Performance-related resources policies

3. Cost-related resource policies

4. Equipment capabilities evaluation

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Decision-Making Tools for Determining

Project Objectives

Brainstorming: to generate a storm of ideas Brainstorming preparation

Brainstorming process

Electronic brainstorming (email, chat, forum, etc.)

Nominal group technique Al of the participants have the opportunity to vote on what they

believe is the most important project objective. All of the participantsare given an equal number of vote to cast.

Delphi process Serves the same function as the nominal group technique. All voting is

conducted anonymously after the brainstorming session hasconcluded. The administrator distributes a list of all of thebrainstorming ideas. The participants then vote for a particular idea.At the end, the administrator retains only a set of the most popularideas.

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chapter 2 - problem formulation

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