The language they understand is months and dollars (or any other type of currency).

The language they understand is months and dollars (or any other type of currency).

Clients, stakeholders and pointy haired bosses really do care about how long a project will take, how much the project will cost and by extension the effort required to deliver the project. What clients, stakeholders and bosses don’t care about is how much the team needs to think or the complexity of the stories or features, except as those attributes effect the duration, cost and effort.  The language they understand is months and dollars (or any other type of currency). Teams however, need to speak in terms of complexity and code (programming languages). Story points are an attempt to create a common understanding.

When a team uses story points, t-shirt or other relative sizing techniques, they hash a myriad of factors together.  When a team decomposes problem they have to assess complexity, capability and capacity in order to determine how long a story, feature or task will take (and therefor cost).  The number of moving parts in this mental algebra makes the outcome variable.  That variability generates debates on how rational it is to estimate at this level that we will not tackle in this essay.  When the team translates their individual perceptions (that include complexity, capacity and capability) into story points or other relative sizing techniques, they are attempting to share an understanding with stakeholders of how long and at what price (with a pinch of variability).  For example, if a team using t-shirt sizing and two week sprints indicate they can deliver 1 large story and 2 two medium or 1 medium and 5 small stories based on past performance, it would be fairly easy to determine when the items on the backlog will be delivered and a fair approximation on the number of sprints (aka effort, which equates to cost).

Clients, stakeholders and bosses are not interested in the t-shirt sizes or the number of story points, but they do care about whether a feature will take a long time to build or cost a lot. The process of sizing helps technical teams translate how hard a story or a project is into words that clients, stakeholders and bosses can understand intimately.

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