todolist # 21 - Bottom up estimation

Till the definition of the schedule, we were doing top down estimation. We decomposed the scope of work into a WBS (work breakdown structure), then decomposed it further into activities. Now it is not a bad idea to estimate the effort requirements at the activity levels, and then roll it up. Ideally, the sum of the efforts of all activities should by and large equal the work package level estimates. In case there is a huge variation, that is an indication of estimation error, either in the top down or in the bottom up estimation and it should be investigated.