Title: The following flow chart and project task duration following table gives estimates using PERT method of estimating the probability of the completion of the project to obtain 14.57 days
| Task \ estimated value | The most optimistic | Most likely | The most pessimistic |
| A | 2 | 3 | 6 |
| B | 4 | 6 | 8 |
| C | 3 | 4 | 6 |
EA = (2 + 3 * 4 + 6) / 6 = 20/6 and EB = (4 + 6 * 4 + 8) / 6, E = (3 + 4 * 4 + 6) / 6
∂ = (value pessimistic - optimistic value) / 6
∂A=4/6、∂B=4/6、∂C=3/6
Seek sum
E = EA + EB + EC = 13.5
∂=（∂A^2+∂B^2+∂C^2）^1/2=1.07
According to the law 3∂
| Interval | Probability |
| (E ∂ , E + ∂ ) | 0.6826 |
| (E-2 ∂ , E 2 + ∂ ) | 0.9544 |
| (E-3 ∂ , E + 3 ∂ ) | 0.9974 |
According to the high school knowledge do the math!
