How to estimate User Stories in Agile when there are unknowns – “How do we know what we don’t know?”

A common problem in Agile sprint planning is estimating stories and planning deliverables when the team just doesn’t know how much effort a particular task will require.  Sometimes, as a Product Owner you will hear things like “well, the complexity of this task depends on several things that we need to research first”, or “we’ll know how complex it is as soon as we start coding”, or even “this type of task is impossible to estimate.  This type of work doesn’t lend itself to Agile estimations”.

The way around these objections is to help the team break down what they know and what they don’t know.  Usually, what they don’t know is easily encapsulated in a bit of research, and that research in turn is fairly easy to estimate.  For example, the PO could ask, “how much research is necessary to understand the approach you will take?”.  The answer might be “…about 1 day, then I will know whether I’ll take approach a or approach b.”  Then you might ask, “worst case, what is the level of effort for those 2 approaches?”.  The answers to those questions should allow the team to estimate the level of effort required to uncover what they don’t know, and then implement their preferred approach.

A real world example might be if you asked me how long it will take me to drive to the airport next Thursday.  I might be inclined to say “I cannot answer that.  There are too many variables.  In a perfect world, I could get there in 20 minutes, but with traffic it’s probably closer to an hour.  If there is an accident on the freeway, it could take as much as 2 hours”.  So, while I am claiming that I have no idea how long it will take me to get the airport next Thursday, I actually have all the information I need to properly plan my trip.  I know it could take as long as 2 hours to get there, so 2 hours before I need to leave I check Google Maps for traffic and get an estimate of my drive time.  If there are no accidents and the estimate is less than an hour, I will check back a little later to get an updated drive time estimate.  I keep checking until I get an estimate that I can live with, and leave my house.  I get to the airport on time, almost every time because I know my worst case drive time, and I know how to solve the problem of dealing with traffic.

Apply this technique at your next planning session, and good luck!

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