Is it bigger than a breadbox?

In the waterfall method of project management, we are asked to estimate how long a large piece of functionality will take to complete.  Then, all of those parts are added up to get a timeline of when things will be done, and we’re off.

As humans we can estimate how long a small, simple task will take relatively accurately.  When that task becomes larger, and/or more complex, we rapidly get worse at estimation.

Agile methodologies ask us to break the tasks down into smaller bite-sized pieces, which allows us to more accurately estimate how long a task will take.  If this is true, then why do people still do relative sizing in agile projects where the tasks are broken down appropriately?


Where both of these systems fail is when you take into account who is doing the work.  We all know that each developer works at a different speed.  There is often a strong correlation between the speed at which a developer can complete a task and their experience level (though, there are certainly times when this is not true).

So, now let’s imagine that we have a team of 5 developers and a rather large project we want to complete.  When we go to estimate, who’s estimate do we take?  Do we go with the lowest estimate, the highest, an average?  Do we divide the work up among the developers and get them to estimate the work they are assigned and hope we divided fairly evenly?  What about vacations, sick time, or someone leaving the company?

Relative sizing to the rescue!

Ok.  So, like anything this is not a panacea.  It works, but it takes effort and commitment to make it work.  Let’s start with a definition of relative sizing.

Relative sizing is simply the process of looking at the stories and determining how big a task is in comparison to other tasks.  The nice thing is most people will agree that task a is smaller than task b most of the time.

When doing relative sizing, most teams pick some series of numbers to assign to the sizes (we used powers of 2, others do prime numbers).  When picking numbers, I suggest not using 1,2,3,4… since this is too fine grained (you want some wiggle room).

Now that you have a scale, each team member can give estimates on tasks using these numbers.  When there is a discrepancy between team members, use that as an opportunity to discuss why there are differences.

Sometimes the difference is because the task is unclear, and this gives you an opportunity to clear up any possible misunderstandings.  Sometimes one developer knows something the others don’t and he/she gives a very different estimate.  This is a good learning opportunity.  Sometimes you will have very small discrepancies, like one developer estimates a 2 and the other a 4, there may not be any differences in understanding, just one thought it was bigger than the other, in that case we typically went with the larger estimate, though you can make your own rules.

You may be wondering how assigning tasks points is going to help you determine when a project will get done. Good! Because I haven’t shared that yet.

After you have points assigned to your cards you will need to plan out a couple of iterations (a defined period of time to do work, often 2 weeks).  Ask the developers how much they think they can do in this iteration and only put in the tasks they think they can accomplish.  After a couple of iterations, you can add up the total points the team completed and take the average.  That will be their velocity.

You will notice when a team first starts out their velocity will probably fluctuate as they get used to estimating and working on the new project.  Be sure to keep an up to date feel for their velocity.  I would recommend not using all of the previous iterations for the average since you may have some anomalies especially at the beginning.

With their velocity and the stories estimated for the project, you should be able to project when a project will be complete.  And, you don’t have to go to all of the trouble of assigning out tasks to individuals!