Lily works as a project manager for BlueWell Inc. She has recorded the following duration estimates for an activity in her project: optimistic 35, most likely 50, and pessimistic 95. What time will she record for this activity?
This is an example of three-point estimate. A three-point estimate records the optimistic, most likely, and the pessimistic duration and then records an average for the predicted duration Three-point estimate is a way to enhance the accuracy of activity duration estimates. This concept is originated with the Program Evaluation and Review Technique (PERT).
PERT charts the following three estimates:
Most likely (TM): The duration of activity based on realistic factors such as resources assigned, interruptions, etc. Optimistic (TO): The activity duration based on the best-case scenario Pessimistic (TP): The activity duration based on the worst-case scenario The expected (TE) activity duration is a weighted average of these three estimates: TE = (TO + 4TM + TP) / 6 Duration estimates based on the above equations (sometimes simple average of the three estimates is also used) provide more accuracy. Here, it is, TE = ( 35 + 50*4 + 95) / 6 = 330/6 = 55