Chapter 8
Planning for Incorrect Predictions

Sponsoring executives use estimates made prior to starting a project to determine if it will fit into their investment criteria. Project managers use estimates at the beginning of a project to build their plans of how to conduct the project in a way that meets the budget and time targets that have been set. These estimates, done when you know the least, are hard to do well and become less valuable over time. Yet we often try to manage the work using these stale estimates as a guide.

Since we know that estimates are not perfect predictions of the future, it seems foolish to do them once and then trust them. In fact, you can use them to get early warnings of your mistaken assumptions. This makes your “wrong estimates” valuable—valuable enough that you might want to create additional estimates specifically as hypotheses to test your assumptions.

When a milestone is missed, it’s an easy reminder to revisit your assumptions. Wouldn’t it be nice to notice before a public milestone is missed? What do you do when things seem to be going smoothly?

You can, of course, wait until there’s a problem. If there’s nothing critical relying on your milestones, that might be the most reasonable approach. Of course, if that’s the case then you might not have needed the estimate at all. Be careful, however, that you’re not overlooking someone else’s important needs.

Most of the time there are consequences for missing a milestone. Those consequences might be minor, such as disappointing a stakeholder or delaying another team, or they might be major, such as missing a market window or incurring legal penalties. The nature of those consequences affects how much effort a development team or project manager may want to invest in prudence.