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.