Estimating Project Size with Story Points
Story points are an estimation tool largely used within the Agile project management methodology. Story points are a relative measure of size of a task or feature, rather than a physical measure such as 'man hours'.
Floor space estimation
Humans have difficulty creating estimates, however relative estimates are considerably easier to accomplish. Estimating the floor space of the room you are currently in would be difficult, however estimating its relative size to the room next door is easier. Is it half as big or twice as big for example? After making your estimate that the room is half as big, if you then discover that the room next door is 40 square feet, it is easy to derive an estimate that your room is 20 square feet.
Story points are relative
Story points work by establishing a standard value of complexity for a common task, and creating estimates for other tasks compared to this standard. The preparing of different types of fruit for consumption is commonly used as an example. If we were to suggest preparing a banana for consumption by peeling it is considered a 4, we could create a relative estimate for the preparation of other types of fruit. Eg:
Through our estimations we may say that peeling a banana constitutes 4 story points. A grape only 1 as it needs no preparation, and a pineapple 20 as it requires 5 times as much effort to prepare as a banana.
Story points allow for the estimation of the 'size' of a feature or task. Velocity is the amount of story points that a team completes during an iteration.