Bottom-up Analysis is a kind of synthetic analysis that aims to improve accuracy of the overall estimation process. This technique uses task decomposition as the basis for making time estimations. The key idea is that a larger task or activity can be decomposed into very small work packages or sub-tasks. Ideally activity decomposition needs to be as deeper as possible, because when work packages are tinier it is easier to estimate their durations.
The advantage of using bottom-up analysis in duration estimation is that the analysis provides a simple and flexible enough estimation method that can be generally applied to any working environment. The disadvantage is that the analysis is very time-consuming. The limitation is that poorly defined tasks cannot be decomposed and estimated efficiently.
The following list explains general steps for performing bottom-up analysis in estimating task duration:
- Indentify a larger task to be estimated
- Be sure this task is clearly defined (inputs, resources and outputs are defined and available)
- Decompose the task into smaller packages or sub-tasks
- Identify and define goals for each of the sub-tasks
- Estimate time required to perform goals of every individual sub-task
- Set start time and finish time for every individual sub-task
- Create an individual time estimate for each of the sub-tasks
- Use individual time estimates to sum up durations of all sub-tasks
- Develop duration estimate for the task.