Hi,
The critical path method, or CPM, was developed by DuPont, to analyse the process of shutting down plants for maintenance, then restarting them at the end of the maintenance cycle. The process involved in this was so complicated, that the critical path method had to be developed to identify and prioritise the vital activities. Similar to a Gantt chart, the CPM provides a graphical representation of the project, and the times expected to complete each activity. However, the CPM does not fix the start and end times of each activity; rather it is used to determine the activities which fall on the critical path. The critical path is the path where all activities directly follow each other, and hence there is no idle time. As such, the length of the critical path determines the total time taken for the project.
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http://www.ukessays.com/mba/project-...ath-method.php