W 12_Said Alamri _Three point Estimation for a Maintenance Project

1. Problem Recognition

With reference to my 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.

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 weeks
  • optimistic (O)=5 weeks
  • most likely (M)=7 weeks

The formula for three point estimate will be applied to determine the time duration of the project: (O + 4M + P)/6).

4. Selection of Criteria

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

5. Analysis and Comparison of the Alternative

Table-1 shows the three point estimate with the mean calculated:

Table-1 Three point estimate calculation

Table-1 Three point estimate calculation


6. Selection of the Preferred Alternative

The estimated time for the project is calculated to be 8 weeks 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. 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/

One thought on “W 12_Said Alamri _Three point Estimation for a Maintenance Project

  1. Said, using the mean only gives you P50…. Which means half the time it will take you longer and half the time you will finish in less time. If the best you can do is P50, I don’t need a project manager, all I need is a coin to help me make decisions……

    There is a KEY POINT missing…….. What is your management’s tolerance for RISK? (and I can almost guaranty you it is NOT P50!!) You need to find out what their tolerance for risk is and then referencing a z Table, tell us how many standard deviations you need to give them the “buffer” or “contingency” they are looking for.

    Explained another way, while you have demonstrated that you know how to use the PERT formula, what this posting tells me is you really don’t fully understand how to USE it effectively.

    Try again…..

    Dr. PDG, Muscat

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