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PERT Calculator

Find a PERT time estimate and its standard deviation.

Calculated Output

Expected time 6.667

Standard deviation 1.333

Formula: E = (O + 4M + P) / 6; SD = (P - O) / 6

Step-by-Step Breakdown

1. Values used:

2. Optimistic = 4

3. Most likely = 6

4. Pessimistic = 12

6. Expected time = 6.667

7. Standard deviation = 1.333

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The math behind it

Expected time = (optimistic + 4 x most likely + pessimistic) / 6. SD = (pessimistic - optimistic) / 6.

O 4, M 6, P 12 give an expected 6.67 with SD 1.33.

Why weight the most likely by 4?

It reflects that the realistic estimate is the most probable outcome.