Estimation the agile way

"The primary purpose of software estimation is not to predict a project’s outcome; it is to determine whether a project’s targets are realistic enough to allow the project to be controlled to meet them."—Steve McConnell, Software Estimation: Demystifying the BlackArt


Estimate means
• To calculate approximately the amount of work
• To form an option about.

But people often treat estimation as the actual figures and commit to some work. This often leads most projects into trouble.

In agile, it is accepted that the initial estimations aren't to be trusted but at the same time it also understands that some expectations need to be set and budgets need to be created.


To make this happen we use the Stories and a concept of Relative Sizing.


User Stories are short descriptions of features our customer would like to see in their software.


Estimating relatively is something we are good at. Let’s say we have two balls in front of us we can easily say how much big one ball is than other. But we might be in a soup if asked to tell exactly how much bigger it is.


Relative sizing can be achieved by using point-based system. Using this approach our measure is always relative not absolute. Here units of measure don’t matter.


All we are trying to do is to capture the size of the task.


Let’s say we some category as follows

Now want we do in relative sizing is as a team we take each story discuss about it and each person in the team will rate some point against that story. If all persons in the team rate the same point they finalize it and move ahead. If there are some dissimilarities they will talk among themselves and justify and try to convince others why the point were given and finally after discussion all will be coming to once conclusion and arriving at a point.


Planning poker is one good example of doing the relative estimation. For more details about planning poker check out this link http://en.wikipedia.org/wiki/Planning_poker


Some advantages of using relative sizing is


• It reminds us that our estimates are guesses.


• It is a measure of pure size. They are more accurate and have less variation.


• It’s fast, better, and cheap

For more information how story point is better than hours check this out


Story Points: Why are they better than hours?