W 12.1_Said Alamri _Three point Estimation for a Maintenance Project

1. Problem Recognition

With reference to my w12 & w3.1 posted blog Cost Estimation for a Maintenance Project, my company encountered leak in fire water pond. The fire water pond bottom material is rubber liner. It is proposed to do permanent solution to overcome the problem for ever. The solution is to make the bottom of the pond concrete instead of existent rubber liner. In the previous blog(w3.1) cost estimation done for the project. In this blog project duration will be estimated using Three Point Estimate method with Probability of 95.

2. Development the Feasible Alternative

Three point of estimate represent the estimated time to complete the project based on:

  • The most pessimistic (P) case when everything goes wrong
  • The most optimistic (O) case where everything goes right
  • The most likely (M) case given normal problems and opportunities .

3. Development of the Outcome for Alternative


  •  pessimistic (P) =15
  • optimistic (O)=5
  • most likely (M)=7 
  • The formula for three point estimate with P95 will be applied to determine the time duration of the project.

4.Selection of Criteria

The estimated time which will result from three point of estimation with P95 will be considered

5. Analysis and Comparison of the Alternative

Table-1 shows the three point estimate with the mean calculation and project duration with P95:


Table-1 Three point estimate calculation

Table-1 Three point estimate calculation


From Z- table Z=1.65

Mean + (Standard Deviation* P95)= 10.75 weeks

6. Selection of the Preferred Alternative

The estimated time for the project is calculated to be 10.75 weeks with P95 for completion of the project.

7. Performance Monitoring and the Post Evaluation of Result

In this bog the time was estimated for the maintenance project with probability of 95. The results will be represented to management for approval.

8. References:


  1. David Kohrell PMP: PERT Formula, retrieved on 25 August 2014 http://www.pmhub.net/wp/2011/02/david-kohrell-pmp-pert-formula/
  2. 4 Tools to Estimate Costs in the Project Management retrieved on June 18, 2014  http://pmstudycircle.com/2012/06/4-tools-to-estimate-costs-in-the-project-management/
  3. W 3.1_Said Alamri _Cost Estimation for a Maintenance Project, retrieved on 25August 2014 https://pmioman14.wordpress.com/2014/06/29/w-3-1_said-alamri-_cost-estimation-for-a-maintenance-project/

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