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GERT Graphical Evaluation & Review Technique By: Pooja Gupta U06CE076 B.Tech-IV Civil Heavy Constructions and Project Management  Presentation


GERT A network analysis technique used in project management. It allows probabilistic treatment of both network logic and activity duration estimated. The technique was first described in 1966 by Dr. Alan B. Pritsker of Purdue University and WW Happ. Compared to other techniques, GERT is an only rarely used scheduling technique.

The use of visual information to predict sales patterns typically involves plotting information in a graphical form. It is relatively easy to convert a spreadsheet into a graph that conveys the information visually. Trends and patterns of data are easier to spot, and extrapolation of previous demand can be used to predict future demands. This procedure makes it possible to analyze complex systems and problems in a less inductive manner and should stimulate efforts in the network analysis area.

Components : 

Components It is composed of:  Exclusive-OR Inclusive-OR AND nodes (vertices) Multi-parameter branches (transmittance edges)

Branches of the network are described by two or more parameters:  Probability that the branch is taken, Pa, given that the node from which ity is emanated is realized . Time, Ta, required, if the branch is taken, to accomplish the activity which the branch represents.

3 realizations on the input side are: : 

3 realizations on the input side are:

On the output side, 2 relations are: : 

On the output side, 2 relations are:

Example : 


Steps in GERT: : 

Steps in GERT: Convert a qualitative description of a system or problem to a model in network form. Collect the necessary data to describe the branches of the network. Obtain an equivalent one-branch function between two nodes of the network.

Slide 12: 

4. Convert the equivalent function into the following two performance measures of the network: The probability that a specific node is realized; and The M.G.F of the time associated with an equivalent network; 5. Make inferences concerning the system under study from the information obtained in 4 above.

Applications: : 

Applications: Network with multiple loops. Network with multiple input and output nodes.

Advantages: : 

Advantages: Graphical. Easy to understand and analyse. Has stochastic approach. Accuracy.  Considers both deterministic as well as probabilistic approach.

References: : 

References: GERT by A. A. B. Pritsker Eisner, H., " A Generalized Network Approach to the Planning and Scheduling of a Research Program", Op. Res., Vol. 10, No. 1, 1962. Parzen, E., Stochastic Processes, Holden-Day Inc., San Francisco, California, 1962.