Critical Path Method
Introduction: Any project time duration can be probabilistic and deterministic in nature.in critical path method the estimation of time is related to cost and a particular uncertainty.
Critical path method:
In critical path method, the time duration of activity is deterministic in nature i.e. there will be a single time, rather than three time estimates as in PERT networks. The network is activity oriented.
Difference between CPM and PERT:
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CPM |
PERT |
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(a) Network is constructed on the basis of jobs or activities (activity oriented). |
(a) Network is constructed basing on the events (event oriented) |
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(b) CPM does not take uncertainties involved in the estimation of times. The time required is deterministic and hence only one time is considered. |
(b) PERT network deals with uncertainties and hence three time estimations are considered (Optimistic Time, Most Likely Time and Pessimistic Time) |
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(c) CPM times are related to cost. That is can be by decreasing the activity duration direct costs increased (crashing of activity duration is possible) |
(c) As there is no certainty of time, activity duration cannot be reduced. Hence cost cannot be expressed correctly. We can say expected cost of completion of activity(crashing of activity duration is not possible) |
CPM Network:
First, one has to establish the logical relationship between activities. That is predecessor and successor relationship, which activity is to be started after a certain activity. By means of problems let us see how to deal with CPM network and the calculations needed.
Example:(CPM) A company manufacturing plant and equipment for chemical processing is in the process ofquoting tender called by public sector undertaking. Help the manager to find the project completiontime to participate in the tender.
(1) Write the network referring to the data
(2) Number the events as discussed earlier.
(3) Calculate TE as done in PERT network TE j = (TEi TE ij)]
(4) Identify the critical path
Project completion time = 20 weeks and the critical path = A – D – F – H.