scientific estimation

This is a follow-up post of my previous post 8 ways to meet budget in Fixed Price Projects.

We can successfully execute and deliver the project within specified time and budget by estimating the size of the project scientifically. There are upteen estimation techniques and they are different for different industries. And within a industry they vary with project domain. But there is a commonaliy among them. All of them are based on some scientific/statistical premise. We as project managers should employ at least one of them and scruplously ensure following:
1. Estimate – Estimate right at the begining of the project.
2. Re-estimate – Estimate in-betwwen the project, if needed or as guided by organizational philosophy.
3. Learn – Compare estimates with actual data at the end of project.
4. Histoy – Maintain historical data and refer to it for estimation.
5. WBS – Use WBS even if you are using a formal estimating methodology. It is a great tool for validating scope and estimating both cost & time.
6. Environment – Be wary of assumptions and constraints. Include their impact in your estimates.
7. Don’t Guess – Avoid very high level comparisons, estimates and gut-feel.
8. Add reserves.

Is estimation a science or an art? It is both. The science can be learned but art comes only with experience.

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  1. I read an article a few days ago written by you where you described 4 different types of estimating, Parametric, Analogous, Bottoms up and I lost the other. It must have been on a Blog that I now cannot find. What was the 3rd one you listed? Bottoms up was the last. Can you let me know the 3rd one and give me the name. Thank you so much

    1. Hi Howard, Thanks for following up on my blog. I am not sure which blog article you referred to but following are the different estimation tech:
      1. Expert Judgement
      2. Analogous Estimation
      3. Parametric Estimation
      4. 3-point Estimation

      Bottom-up estimation is broader technique that uses one of the above 4. Let me know what other info do you need.


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