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Seeing How Well a Team’s Story Points Align from One to Eight

by Mike Cohn, 19 September 2011 | Agile Estimating

This post is from Mike Cohn's Blog - Succeeding With Agile® by Mike Cohn. Click here to see the original post in full.

The topic of how well a team estimates two point stories relative to one point stories (and so on) has come up in a couple of comments and replies on this blog recently, so let’s discuss it. Here’s a graph showing relevant data from one company:

A graph showing the measured relationship between points and hours

Each column of data and pair of bars shows data from stories of the size given in the Points row. The first set of data is for one-point stories, the second set of data is for two-point stories and so on. Looking at the one-point data, we see that the median number of hours to complete a one-point story (at this company) was 21 hours. The shortest (From) took 6 hours and the longest (To) took 36 hours. The shortest and longest are shown in the green and blue bars above the table. The median is graphed as the red line.

Let’s look at the two-point stories. We see there a median effort of 52 hours and a range from 31 to 73. If we assume the 1-point stories were perfectly estimated, we would expect 2 point stories to have a median of 42 instead of the 52 we see here. Or perhaps the 2-point...

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