6.3.1 PERT technique continued

Using the formula for  Te= (a+4m+b)/6 and σ2= (ba/6)2, the estimated times and variances are completed as shown in the this table.

Activity

Predecessor

a

m

b

Expected Time

Variance

A

6

7

14

8

1.78

B

8

10

12

10

0.44

C

A

2

3

4

3

0.11

D

A

6

7

8

7

0.11

E

B,C

5

5.5

9

6

0.44

F

B,C

5

7

9

7

0.44

G

D,E

4

6

8

6

0.44

H

F

2.5

3

3.5

3

0.03

We can now determine the completion time and critical path as before. The answer is shown herepert-techniquex

From the network diagram, the estimated project completion time is 23 weeks

Verify for yourself that the critical path is A, C,E, G. See diagram here pert-technique-with-cpx

This means we have a 50% probability of completing the project in 23 weeks or less.

Now, what will be the probability of completing the project in say 25 weeks, or 20 weeks? go to the next page to find out how we answer these questions.

Leave a Reply