PERT analysis is based on

1) Optimistic time
2) Pessimistic time
3) Most Likely Time

1)Optimistic time: This is a best-case scenario. Here the estimate is determined by considering all favorable conditions. This is the shortest duration to complete the task.

2)Pessimistic time: This is a worst-case scenario. Here the estimate is determined by considering all unfavorable conditions; the longest time the activity may take to complete.

3)Most Likely Time: The cost/duration of the activity, based on a realistic effort assessment for the required work and any predicted expenses. The chance of completing an activity is highest within this duration.

Probabilistic time for completion of any activity can be found out from
* optimistic time
* pessimistic time
* most likely time