Task estimating: completion time versus team size

A careful estimate of a certain task indicated that it could be completed by four engineers in six months, so the completion effort was twenty-four engineer-months. It is logical to assume therefore that six engineers will complete the task in four months, and eight engineers in three months. The author shows that this assumption is wrong, and offers a reason as to why this is so. The article shows that the human effort required to complete a divisible task is a function both of the nature of the task and of the number of people assigned to it. The fact that task team size enters into effort-to-complete calculations both exposes the widely-employed constant effort fallacy and substantially complicates the estimating problem. The estimating technique presented here is a useful and pragmatic solution to this problem. It turns on the twin concepts of a sparse ´minimum people´ estimate and a factor which measures task complexity and the degree of sub-task coupling.<>