Question

A PERT network has 9 activities on its critical path. The standard deviation of each activity on the critical path is 3. The standard deviation of the critical path is

• A. 27
• B. 9
• C. 3
• D. 81

Answer 1

The correct option is B 9

In CPM,

$\sigma =\sqrt{\text{sum of variance along critical path}}$

$\sigma =\sqrt{{\sigma }^2+{\sigma }^2+.....+{\sigma }^2}$

$\sigma =\sqrt{9{\sigma }^2}=\sqrt{9\times 9}=9$