Critical path analysis (A level BS)

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Also generally refered to as Network Analysis, it is used so managers of companies can plan projects as effectivly as possible to ensure that time and resources are not wasted. They do not want people or machines sat idle in the corner or materials delivered before or at worst after they are needed. To help them with this planning programme they often use Critical Path Analysis.

Network analysis is a method of organising the diffrent activities involved in a particular process in order to find out the most efficient means of completing the task. The aim being to complete the task in as shorter duration as possible. To make this possible the firm must firstly identify the exact order in which the activities will have to be undertaken, and which activities can be run simulataneously to save time.

The CPA was first developed for DuPoint in 1957 to speed up the building of the new plant, today, it is carried out by thousands of companies all over the world.

In Order to carry out a CPA you must :-

• Identify all the diffrent tasks involved in the process
• Estimate the expected length of time each task will take
• Determine the order in which tasks must be completed

During the CPA you will find there are some "dependant activities" theses activities are ones which cannot be completed untill another activites has been carried out before hand. "Parallel activities" are ones which can be carried out at the same time as others.

The first main step toward constructing a CPA is to construct a network chart. This is a diagrammatic representation of all the activities involved in the project, the order in which they are undertaken and how long they are estimated to take.

When drawing a Network diagram the following features are used - A "Node" - A Circle representing the start and finish of each activity; a straight line representing the activity itself. Below the line is numbered the amount of days they have estimated it to take, above the line the task is named (often a letter)

When construsting a chart its important that you must remeber the follwoing

• The lines showing diffrent activities must never cross.
• The lines showing activities should always begin and end with one node
• When drawing the activities and nodes do not put the end node on any activity untill you are sure what comes next .

After this you will of formed a basic CPA, however there are a few more things you must consider before fully completeing a CPA. The next stage is producing a network chart in order to show various information which can be calculated from the duration of each activity. The Node is split into 3 sections, in half and on the left hand half, in half again. In the right half you list the number of the node and in the two remaining quarters you list what is called the "Earliest start time" and "Latest finish time" also known as "EST" & "LFT" These are exactly what they say they are, and are calculated to find out the earliest possible time it can be complated or the latest finish time, this halps the company see if any "float" time will be made available. To find out the total float time the following equation is used Total Float Time = LFT - Duration - EST. Through this the critical path can be identified which is the activities that have no float time and if they are overun the whole project will be held back in terms of duration. This is often marked with a red pen along the lines appropriate on the CPA Grid.