Why do we estimate work? Traditionally, estimates help project managers and business owners cost a project. Time and effort to perform tasks factor into per-person daily cost which, when added up, provide a high level view of the dollar value of investment needed.
Adding up hours for tasks, though, is highly inaccurate and error prone.
Flaws in traditional estimation
- Tasks are not independent of each other.
- Hour-based estimation is too precise and lacks recognition of natural variation.
- Estimation is influenced by optimism bias.
- Estimation is often undertaken by an expert and not the people who will do the work.
Improving estimation using agile techniques
Agile forms of estimation are typically based on the wideband delphi technique developed in the 1950-1960s at the RAND Corporation as a forecasting tool. Its method of classifying effort by groups and then deriving time is the basis for agile estimation using planning poker.
- Recognise the pros and cons of different methods of estimation.
- Understand the role of the Definition of Done in estimation.
- Apply the planning poker technique to team work.
- Define velocity and apply it to forecasting work.
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Problems to watch out for