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What is PERT?? - Advantages & Disadvantages



What is PERT


PERT is Program Evaluation and Review Technique that is used in construction and project management field. This is a project network analysis technique that is used to undergo planning and controlling of the projects. 


The PERT technique focuses on the time and the cost each activity takes. This will hence influence the resultant time and the cost required for the completion of the entire project. This network analysis technique helps to understand the performance of the work throughout the course of the project.

Fig.1: A PERT Network; tE = estimated time for each activity shown on each activity row


PERT is an event oriented project scheduling technique. This method of networking will not show any kind of interdependencies between the events mentioned in the network. The network represents a combination of the event. An event is represented in terms of time and resources that are required for the completion of that event. The PERT network does not have a historic chain as in the case of Critical path method (CPM). 


Note: The PERT technique is more applicable to the projects that are newly faced, where most of the events are employed the first time or by means of a new technique. This is applied on projects that have no repetitive nature.


The PERT technique possess many advantages that facilitate the project team and many disadvantages that have to be taken care by the project managers. The pros and cons of PERT are mentioned below.


Advantages of PERT


The advantages of PERT are mentioned below:

  1. Planning For Large Projects
  2. Visibility of Critical Path
  3. Analysis of Activities
  4. Coordinating Ability
  5. The What - if -Analysis

Planning For Large Projects: The scheduling of project activities is done easily with the help of PERT system by the project manager. This technique is more active in large sophisticated project works. As PERT is event oriented programming technique, three elements are necessary to define an event. They are:

  1. What is the time required to perform the event?
  2. What comes after the event?
  3. What is coming before the event?
The answers to the above question make the scheduling easier and clear.


Visibility of Critical Path: The PERT method will show the critical path in a well-defined manner. The critical path is the path with activities that cannot be delayed under any circumstances. A proper knowledge about the stack values with limited conditions of dependencies will help the project manager to bring fast and quality decisions that will favor the project performance.

Analysis of Activity: The activity and the events are analyzed from the PERT networks. These are analyzed independently as well as in combination. This will give a picture about the likely completion of the project and the budget.

Coordination: The various departments of the construction organization will deliver data for the PERT activities. A good integration is developed between all the departments which will help in improving the planning and the decision-making capabilities of the project team. The combination of qualitative and quantitative values from a large amount of data will help in improving the coordination of the project activities. This will also improve the communication between various departments of the organization.

What - if -Analysis: The possibilities and the various level of uncertainties can be studied from the project activities by properly analyzing the critical path. This type of analysis is called as what-if-analysis. For this various sets of permutation and combination is conducted. Among them, the most suitable combination is taken into consideration. This set chosen will be the one with minimum cost, economy and best result. This analysis helps to identify the risk associated with any activities.


Disadvantages of PERT

Various Demerits of PERT are mentioned below:

  1. Time Focused Method
  2. Subjective Analysis
  3. Inaccuracy due to Prediction
  4. Expensive 
  5. Other Issues
Time Focused Method: The method of PERT is a time oriented method, where the time required to complete the respective activity is of higher importance. Hence the time determination of each activity and its allocation is very much necessary. This is done based on an assumption and within this time the work will be completed. If this is not the case issues will arise.

Subjective Analysis: The activities for a project is identified based on the data available. This is difficult in case of PERT as these are mostly applied for a project that is newly conducted or those without repetitive nature. The project dealt by PERT will be a fresh project data that make the collection of information to be subjective in nature. This will bring less accuracy on the time and the estimated time.
         There are chances to have inaccuracy and bias in the sources of data. This makes it unreliable. As this is not repetitive in nature, there is no sense in bringing the records from the past historical data.

Prediction Inaccuracy: As there is not past records or assistance to bring an outline for the project, predictions take their role. The overall project may move to total loss if the predictions and the decisions are inaccurate. No trial and error method can be employed.

Expensive: As this method is carried out based on predictions in overall, they find too expensive in terms of methods employed, the time consumed and the resources used.

Other Issues: This method is highly labor intensive in nature. As there are chances of increase in project activities large and complicated networks are developed as many task dependencies come into existence. If two activities share common resources, this technique won;t find very apt for the project. 

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