Question

A project consists of two activities A and B. The most optimistic and pessimistic time for completionn of project is shown in the table below.

Acitivity	Optimistic Time	Pessimistic Time
A	1 hr	3 hr
B	2 hr	5 hr

The standard deviation for the project is:

• A. 0.91
• B. 0.83
• C. 0.36
• D. 0.6

Answer 1

The correct option is D 0.6

Variance ${\sigma }^2={\left(\frac{t_p-t_0}{6}\right)}^2$

Variance for activity A, ${\sigma }_A^2={\left(\frac{3-1}{6}\right)}^2=0.11111$

Variance for activity B, ${\sigma }_B^2={\left(\frac{5-2}{6}\right)}^2=0.25$

Standard deviation for project $=\sqrt{{\sigma }_A^2+{\sigma }_B^2}=\sqrt{0.111+0.25}=0.6$