Page 231 - DMGT521_PROJECT_MANAGEMENT

Project Management

Notes for all available paths. Activities that have slack can be delayed without changing the overall
time of the project. Slack is computed in one of two ways, slack = LF - EF or slack = LS - ES.
Activities that are on the critical path have a slack of zero (0).
1. The duration of path adf is 14.83 work days.
2. The duration of path aceg is 19.51 work days.
3. The duration of path beg is 15.67 work days.

4. The critical path is aceg and the critical time is 19.51 work days. It is important to note that
there can be more than one critical path (in a project more complex than this example) or
the critical path can change. For example, let’s say that activities d and f take their pessimistic
(b) times to complete instead of their normal (T ) times. The critical path is now adf and the
E
critical time is 22 work days. On the other hand, if activity c can be crashed to one work
day, the path time for aceg is reduced to 15.34 work days, which is slightly less than the
time of the new critical path, beg (15.67 work days).
Assuming these scenarios do not happen, the slack for each activity can now be determined.
Start and finish are milestones and by definition have no duration, therefore they can have
no slack (0 work days).
The activities on the critical path by definition have a slack of zero; however, it is always
a good idea to check the math anyway when drawing by hand.

(a) LF - EF = 4 - 4 = 0
a a
(b) LF - EF = 9.17 - 9.17 = 0
c c
(c) LF - EF = 14.34 - 14.34 = 0
e e
(d) LF - EF = 19.51 - 19.51 = 0
g g
5. Activity b has a LF of 9.17 and a EF of 5.33, so the slack is 3.84 work days.
6. Activity d has a LF of 15.01 and a EF of 10.33, so the slack is 4.68 work days.
7. Activity f has a LF of 19.51 and a EF of 14.83, so the slack is 3.84 work days.
Therefore, activity b can be delayed almost 4 work days without delaying the project. Likewise,
activity d or activity f can be delayed 4.68 work days without delaying the project (alternatively,
d and f can be delayed 2.34 work days each).

Figure 13.11: A Completed Network Diagram Created using Microsoft Visio

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