A PERT network has three activities on critical path with mean time 3, 8 and 6 and standard deviations 1, 2 and 2 respectively. The probability that the project will be completed in 20 days is

A PERT network has three activities on critical path with mean time 3, 8 and 6 and standard deviations 1, 2 and 2 respectively. The probability that the project will be completed in 20 days is Correct Answer 0.84

Standard deviation = square root of (variance) = square root of (1 * 1 + 2 * 2 + 2 * 2) = square root of (9) = 3
D = 20
S = 3 + 8 + 6 = 17
Probability $$ = \frac{{\left( {{\text{D}} - {\text{S}}} \right)}}{{{\text{standard deviation}}}} = 1$$
Now, from Z table probability = 0.84.

Related Questions

Statement (I): Crashing of project duration always increases the cost of the project on its completion, no matter what the indirect, or overhead, costs are. Statement (II): The critical path along the project activities network diagram is compressed in the process of investigating the crashing of the project duration, and not the non-critical activities, up to a certain stage of crashing.