There are four activities on the critical path.Coincidentally,the standard deviations for their durations are all equal to 4.The standard deviation of the duration for the critical path is therefore equal to:
A)2
B)4
C)8
D)16
E)64

Question

Quizplus · Accepted Answer

When activities are on the critical path, their durations are added together to find the total duration. However, when calculating the standard deviation for the critical path, you add the variances of the individual activities (not the standard deviations) and then take the square root of that sum. The variance of each activity is the square of its standard deviation, so for each activity with a standard deviation of 4, the variance is $4^2 = 16$. For four activities, the total variance is $4 \times 16 = 64$. The standard deviation of the critical path is the square root of 64, which is 8.

There Are Four Activities on the Critical Path