Michelle

Posted by admin on February 14, 2018 in Articles

I. A1. Expected Completion Time
ECT is derived using the formula which obviously gives more weight to the “probable” time estimate:Where a = Optimistic time
b = Probable time to complete
m = Pessimistic time
Before allowing for concurrent activities. those that can proceed on parallel tracks, as it were, ECT for the entire project is shown by Table 1 (overleaf) below as 68 ? weeks:Table 1: First Estimate of ECT

a
m
b
Calculation
Expected Time to Complete (weeks)

A
2
3
4
(2+(4×3)+4)/6
3
B
5
6
13
(5+(4×6)+13)/6
7
C
3
4
8
(3+(4×4)+8)/6
4.5
D
10
11
15
(10+(4×11)+15)/6
11.5
E
4
5
6
(4+(4×5)+6)/6
5
F
8
10
12
(8+(4×10)+12)/6
10
G
4
6
11
(4+(4×6)+11)/6
6.5
H
8
10
18
(8+(4×10)+18)/6
11
I
3
6
12
(3+(4×6)+12)/6
6.5
J
2
3
7
(2+(4×3)+7)/6
3.5
TOTAL

68.5But the fact is, there are many possibilities for concurrent project activity. Task B, for instance, can be triggered by project start and has no start-to-finish link with Task A. Task D itself does not depend on tasks A and C being completed; it can proceed as soon as B is done. When one runs through all the concurrent stages, net elapsed time can really collapse to 35 weeks (Table 2 below). Given ECT = ES + t, as well, Table 3 (overleaf) displays the calculations and outcomes which compress project completion to 30 weeks.Table 2: ECT Based on “Probable Time to Complete” and Employing Forward Pass
Preceding Activity
Probable Time to Complete
(weeks)
Earliest Start
Earliest Finish
START

A
START
3
0
3
B
START
6
0
6
C
A
4
3
7
D
B
11
6
17
E
C
5
7
12
F
B
10
6
16
G
F
6
16
22
H
D,E
10
17
27
I
G
6
22
28
J
H,I
3
28
31
END

TOTAL
64

31II. A1a. Schedule Variance
Conceding a degree of uncertainty for each task and employing the formula for variance of activity time:Where a = optimistic time and b =…