Estimating the amount of time needed to complete a task or work package is one of the most important, and trickiest, parts of building any project plan. Tasks that are mis-estimated and on the critical path will have an immediate impact on the project’s schedule and can often snowball as the project continues.
Because many conversations that I have with functional managers or subject matter experts about task estimate start with “Best case scenario” or “Worst case scenario”, I’ve found that three-point estimates provide a bit more accuracy than a single point and are often not difficult to get.
A typical conversation goes something like this:
Me: How long do you think that will take?
Manager: Everything goes perfectly, one day.
Me: What if everything goes wrong?
Manager: Then it could be up to five days.
In that brief exchange, I have my optimistic and pessimistic estimates.I can ask another follow up to get an idea of the most likely number or use the average of the two.After some more conversation about the risks that could cause the large difference, I can feel comfortable that I have a decent estimate.