# A Guide to Network Analysis

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A GUIDE TO NETWORK ANALYSIS

by

MICHAEL C GLEN

Introduction

The core technique available to Project Managers for planning and controlling their projects is Network Analysis. This short guide will provide a basic understanding of networking principles before applying them to the computer.

Network Analysis or Critical Path Analysis (CPA) or the American Ў§Program, Evaluation and Review TechniqueЎЁ (PERT) is one of the classic methods of planning and controlling the progress of projects.

Effective planning of projects requires careful thought and the application of logic. To illustrate this planning tool, let's consider the manufacture of a small item. Some typical processes might be:

cutting

finishing

assembling

machining

testing

designing

All these processes are called ЎҐACTIVITIESЎ¦ or ЎҐTASKSЎ¦

Step 1:

List WHAT has to be done.

Hint: try thinking of verbs ending in Ў§...ingЎЁ, like machining or testing.

Do not consider at this stage who is going to do what, concentrate on WHAT.

An activity or task is represented by a rectangle, thus:

Step 2:

Decide the ORDER in which it is to be done.

Some steps are obvious: we, perhaps, cannot test until assembly has been completed, which cannot be done until the various parts have been made. So we have a logical relationship between the start of one task and the beginning of the next. We could order our list of tasks thus:

designing purchasing cutting machining assembling testing finishing

Logic Network or PERT Chart

Writing this out as a network:

We put the tasks into rectangles and join them with arrows to show the sequence or precedence: the logical relationships between them.

Suppose that once we have bought the materials, some need cutting to size and others need turning on a lathe. The tasks of machining and cutting could run in parallel rather than consecutively, assuming we have the appropriate resources. But let's add a bit more. Say the cut parts need to be welded together before assembling ЎX like this:

Let's add another task: the writing of a set of test instructions. Where would writing fit in? Well, the writing cannot really start until the design is finished, though it could be carried out at the same time as the fabrication, but it must be ready before the testing can begin. Applying such logic to the relationships, we can add the task writing like this:

Now let's say we need to have our draughtsman produce some illustrations for our test instructions. When the writing and the drawing are finished, we will then need to edit the whole:

And so the network is built up, often cuing the mind to missing tasks.

In this step always assume you have infinite resources so that who does what does not cloud the issue ЎV concentrate only on the LOGIC.

Time Analysis

Duration

Having completed the network, we can begin the analysis. Firstly, we need to know the duration of each task

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