PERT ANALYSIS
Activity
|
Predecessors
|
Three time Estimates
|
||
a
|
m
|
b
|
||
A
|
---
|
1
|
2
|
3
|
B
|
A
|
3
|
5
|
7
|
C
|
A
|
6
|
10
|
14
|
D
|
A
|
4
|
6
|
8
|
E
|
B,C,D
|
8
|
9
|
10
|
F
|
E
|
2
|
4
|
6
|
G
|
F
|
1
|
3
|
5
|
STEP-1: CALCULATE
Te.
Te = (a+4m+b)/6
Activity
|
Predecessors
|
Three time Estimates
|
Te
|
||
a
|
m
|
b
|
|||
A
|
---
|
1
|
2
|
3
|
2
|
B
|
A
|
3
|
5
|
7
|
5
|
C
|
A
|
6
|
10
|
14
|
10
|
D
|
A
|
4
|
6
|
8
|
6
|
E
|
B,C,D
|
8
|
9
|
10
|
9
|
F
|
E
|
2
|
4
|
6
|
4
|
G
|
F
|
1
|
3
|
5
|
3
|
STEP-2:
CALCULATE STANDARD DEVIATION (S.D)
S.D = (b-a)/6
Activity
|
Predecessors
|
Three time Estimates
|
Te
|
S.D
|
||
a
|
m
|
b
|
||||
A
|
---
|
1
|
2
|
3
|
2
|
0.33
|
B
|
A
|
3
|
5
|
7
|
5
|
0.67
|
C
|
A
|
6
|
10
|
14
|
10
|
1.33
|
D
|
A
|
4
|
6
|
8
|
6
|
0.67
|
E
|
B,C,D
|
8
|
9
|
10
|
9
|
0.33
|
F
|
E
|
2
|
4
|
6
|
4
|
0.67
|
G
|
F
|
1
|
3
|
5
|
3
|
0.67
|
STEP 3:
CALCULATE VARIANCE(V)
V= (S.D)2
Activity
|
Predecessors
|
Three time Estimates
|
Te
|
S.D
|
VARIANCE
|
||
a
|
m
|
b
|
|||||
A
|
---
|
1
|
2
|
3
|
2
|
0.33
|
0.11
|
B
|
A
|
3
|
5
|
7
|
5
|
0.67
|
0.44
|
C
|
A
|
6
|
10
|
14
|
10
|
1.33
|
0.78
|
D
|
A
|
4
|
6
|
8
|
6
|
0.67
|
0.44
|
E
|
B,C,D
|
8
|
9
|
10
|
9
|
0.33
|
0.11
|
F
|
E
|
2
|
4
|
6
|
4
|
0.67
|
0.44
|
G
|
F
|
1
|
3
|
5
|
3
|
0.67
|
0.44
|
STEP 4:
CALCULATE VARIANCE FOR THE CRITICAL PATH
(neglect
the nodes which are not a part of critical path)
Activity
|
Predecessors
|
Three time Estimates
|
Te
|
S.D
|
VARIANCE
|
VARIANCE OF CRITICAL PATH
|
||
a
|
m
|
b
|
||||||
A
|
---
|
1
|
2
|
3
|
2
|
0.33
|
0.11
|
à 0.11
|
B
|
A
|
3
|
5
|
7
|
5
|
0.67
|
0.44
|
-
(node is not a part of critical path)
|
C
|
A
|
6
|
10
|
14
|
10
|
1.33
|
1.78
|
à1.78
|
D
|
A
|
4
|
6
|
8
|
6
|
0.67
|
0.44
|
-
(node is not a part of critical path)
|
E
|
B,C,D
|
8
|
9
|
10
|
9
|
0.33
|
0.11
|
à0.11
|
F
|
E
|
2
|
4
|
6
|
4
|
0.67
|
0.44
|
à0.44
|
G
|
F
|
1
|
3
|
5
|
3
|
0.67
|
0.44
|
à0.44
|
STEP-5:
CALCULATE TOTAL OF CRITICAL PATH
VARIANCE
Activity
|
Prede
cessors
|
Three time Estimates
|
Te
|
S.D
|
VARIANCE
|
VARIANCE OF CRITICAL PATH
|
||
a
|
m
|
b
|
||||||
A
|
---
|
1
|
2
|
3
|
2
|
0.33
|
0.11
|
à 0.11
|
B
|
A
|
3
|
5
|
7
|
5
|
0.67
|
0.44
|
-
(node is not a part of critical path)
|
C
|
A
|
6
|
10
|
14
|
10
|
1.33
|
1.78
|
à1.78
|
D
|
A
|
4
|
6
|
8
|
6
|
0.67
|
0.44
|
-
(node is not a part of critical path)
|
E
|
B,C,D
|
8
|
9
|
10
|
9
|
0.33
|
0.11
|
à0.11
|
F
|
E
|
2
|
4
|
6
|
4
|
0.67
|
0.44
|
à0.44
|
G
|
F
|
1
|
3
|
5
|
3
|
0.67
|
0.44
|
à0.44
|
TOTAL OF CRITICAL PATH VARIANCE
|
2.89
|
|||||||
STEP-6:
CALCULATE THE S.D OF CRITICAL PATH
S.D = √ (VARIANCE OF
CRITICAL PATH)
S.D
= √2.89
= 1.699
STEP-7:
CALCULATE THE VALUE OF Z
Z = (x - µ) / (S.D)
Z=
(39-28)/1.699 = 6.47
Here,
x= total estimate time ( ∑Te )
µ= ( ∑Te ), includes only the critical path nodes
µ= ( ∑Te ), includes only the critical path nodes
STEP 8:
CALCULATE THE PROBABILITY
PROBABILITY
= NORMSDIST(Z)
PROBABILITY
= NORMSDIST(6.47) = 1 = 100%
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