Question

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

• A. 0.50
• B. 0.66
• C. 0.95
• D. 0.84

Answer 1

The correct option is D 0.84

Estimated completion time $T_{\theta }=3+8+6=17$

Standard deviation, $\sigma =\sqrt{\sum {\sigma }^2}=\sqrt{1^2+2^2+2^2}=3$

$z=\frac{T-T_e}{\sigma }=\frac{20-17}{3}=1$

Probability= 0.84