Estimation

  • Purpose
    • Forecast cost and effort involved in finding the progress of an activity
  • Description
    • Develop a better understanding of possible magnitude of the costs and efforts associated with any initiative, when it’s possible to determine the exact cost
    • Can not eliminate the uncertainty, seeks to achieve reasonable assessment of required costs and efforts
    • The less information, more the uncertainty
    • Revision emerge as more information
    • Support for historical records
    • Important to evaluate the extent of uncertainty
  • Elements
    1. Analogous estimation – Top-Down, use of similar project, is not well known at the beggining of the project, order of magnitude (ROM – rough order of maginitude)
    2. Parametric Estimation – Parameters x number of hours, requires historical as comparative basis (COCOMO II, function points, points of use cases and story points)
    3. Bottom-up estimation– Collects and gathers the deliveries, activities, tasks and estimates for estimating small items
    4. Rolling Wave – Refinement of estimates, review of future deliveries based on what was delivered
    5. Three-Points Estimation – Based on the scenarios (not average):
      • Optimistic
      • Pessimistic
      • The most likely
    6. Historical Analysis – similar to analogous estimating, but used to top-down and bottom-up. Needs historical repository
    7. Evaluation of specialist – experience of internal or external experts
    8. Estimation of Delphi – Combination of  the evaluation of the expert and history (top-down e bottom-up), sharing to the consensus, average of the three estimates
  • Usage considerations
    1. Advantages – Help making decisions based
    2. Disadvantages – Treatment of the estimate as a compromise, usually altered to attend the most influential stakeholders

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