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. 3
• B. 9
• C. 27
• D. 81

Hint:

In PERT networks, the standard deviation of the critical path is the square root of the sum of the variances of the activities on the critical path.

Answer 1

The Correct Option is B

The standard deviation of the critical path in a PERT network is calculated by summing the variances of each activity on the critical path. Since the standard deviation for each activity is given as 3, the variance for each activity is \( 3^2 = 9 \). The total variance of the critical path is the sum of the variances of all 9 activities, so: \[ \text{Total variance} = 9 \times 9 = 81 \] Thus, the standard deviation of the critical path is the square root of 81: \[ \text{Standard deviation} = \sqrt{81} = 9 \] Therefore, the correct answer is (B).