Wednesday, 18 March 2015
Guiding your estimates in the right direction
Problem: Estimating effort for (test-)activities is inaccurate
Estimation, or educated guessing is the foundation for many an activity related to management of a project. Given that estimation is not an exact science there will be inaccuracy in the numbers used for planning and resource allocation.
Solution: Apply general estimation rules and use a technique to guide your estimates.
In order to improve accuracy in your estimation you can rely on some general estimation rules and use a technique to guide your estimation.
General estimation rules:
· A full-time resource will only be productive around 80% of the time.
· Shared resources, working on multiple projects will have a lower productivity given that they will have to spend time when they do context switching.
· There is a high degree of optimism in estimates, as most people have tendency of underestimating complexity and time consumption.
· Base you estimates on multiple sources – Don’t just use own experience, pursue experience of others if possible.
· Estimation of a task should be done by the person/team responsibility for doing the task.
· Remember to include issue management, meetings and other supportive activities in the estimate.
· Break estimates down if possible.
· Make sure that assumptions, exceptions and limitations are clearly documented as part of the estimate
Techniques for estimating
· Top-down estimation
· Bottom-up estimation
· Combined top-down & Bottom-up estimation
· Comparative estimation
· Parameter estimation
· One-point estimation
· 3-point estimation
The point is that there are numerous techniques that allow you to do more or less scientific estimation – You need to choose the one that fits the purpose and tolerance of your project.