Time Estimates
Estimation of these time estimates can be done in two ways.
1. Deterministic Approach: The planner has enough knowledge about the activity and gives a single estimate of the duration, which is almost accurate
2. Probabilistic Approach: The planner does not have many ideas about the activity as there is little or no past history about it.
In order to take into account the uncertainties involved in the activity times, three kinds of time estimates are made for each activity in PERT.
(i) Optimistic time (to): Optimistic time is a concept used in the program evaluation and review technique (PERT). It represents the shortest estimated time period within which a task is likely to be completed, and is used in project planning.
(ii) Most Likely Time (tm): Most likely time, expressed as 'tm', represents estimate of time for completion of an activity, which is neither optimistic nor pessimistic, assuming that things should go in a normal way, and if the activity is repeated several times, in most of the cases, it will be completed in time represented by t.
(iii) Pessimistic Time (tp): Pessimistic time is a concept used in the program evaluation and review technique (PERT). It represents the longest estimated time period within which a task is likely to be completed, and is used in project management activities.
Critical Path: The time-wise longest path is called the critical path. In this path, any type of delay, in any event, will cause a delay to the project. These are shown by double line or dark lines in a network.
An event is critical if its slack is zero.
Event Time
Probability Factor (z)
z = TS -TE/σ
Where, TS = Given scheduled completion time of the project
TE = Expected completion time of the project.
σ = Standard deviation
It is assumed to be a β - distribution curve with a unimodal point occurring at tm and its endpoints occurring at to and tp. The most likely time need not be the midpoint of to and tp, and hence the frequency distribution curve may be skewed to the left, skewed to the right or symmetric.
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1. What is PERT analysis in civil engineering? |
2. How does PERT analysis benefit civil engineering projects? |
3. What are the key components of PERT analysis in civil engineering? |
4. How is a PERT network diagram created in civil engineering projects? |
5. Can PERT analysis be used in conjunction with other project management techniques in civil engineering? |
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