Should We Measure Individual Estimates Accuracy?

Individual estimates accuracy is another metric requested by several TargetProcess users. First of all it may be useful if and only if:

  • Task estimated by one developer only (if whole team estimates tasks you can’t measure individual accuracy, only whole team accuracy).
  • You are using time tracking to track all spent time for all tasks

For example, Ted subscribed to Quick Search user story. He broke down this user story to tasks, estimated each task and got 50 hrs of effort for user story. Then he implemented the user story and spent 60 hrs. It means his estimate accuracy for this task is 50 / 60 = 0.83 or 83%. In the end of iteration we can calculate all Ted’s assignments and spent time and define estimate accuracy for next iteration, let’s say it is 0.7.

OK, but how we can use this metric? Well, if Ted subscribed to 60 hrs work it means he will spend 85 hours and for 2 weeks iteration it means at least 5 hrs overtime. Ted should take this information into consideration and remove some tasks from his ToDo. This works if Ted estimate accuracy remains the same, but is that always the case? In reality Ted’s accuracy may vary from 0.5 to 0.9 and exactly for next iteration it may be 0.9 and in this case Ted will be able to do all committed work.

As you see estimate accuracy coefficient should be used as a recommendation only, but if Ted insists on his commitment Project manager/Scrum master should agree and let Ted do the job. Again we have similar problem as with individual velocity when Scrum master may demotivate developers with numbers in hands.

I see value in individual estimates accuracy, but I see some danger as well. This metric should be used by developers, not by Project managers/Scrum masters.

I think we should care about team estimates and team velocity, not about individual estimates and individual velocity. Agile development is all about gelled teams.

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