Estimating

I was flying home from a client visit last week at the airport getting ready to board the plane when the gate agent announced that the flight was gonna be delayed by ten minutes due to some unspecified mechanical issue. Ten minutes later they announcement another ten minute delay. They did this two more times.

So what was going on? Did the airlines not want to admit upfront that they had a 40 minute delay so they fed the delays to us ten minutes at a time? Or did the person who is doing the work really not understand how long it was going to take? I started thinking about how common it is for people to not be able to provide good estimates. Sometimes they underestimate the complexity, or maybe student syndrome sets in, or they're just overly optimistic.

It was ironic, but part of the work with my client that week was explaining the technique of relative estimates using t-shirt sizes and story points. The team I was working with was  new to agile and used to the old way of doing absolute estimates, which as we all know are not as accurate because of things like student syndrome or Parkinson's Law.

So how do we get better at estimating? I think the real question should be how we recognize estimates for what they are. An uncertain prediction of a future event. Even when we use story points, we won't know our true velocity until after a couple iterations when the team has time to come together. At the beginning of the project, we need to recognize how much uncertainty we have. So instead of saying "that will take about 2 months" we should say "that may take 2 months, but it could take as long as 3 months." So we provide not only the estimate but some measure of the uncertainty that goes with it. Similarly, if we think a story might be 13 points, but there's a lot of uncertainty, we should state that and make the story 20 points (or 21 if you're being strict with your Fibonacci sequence). Now if only I could get the airlines to provide a more accurate estimate the next time there's a delay...or at least how certain they are!