What Makes a Good Plan?
A good plan is one that stakeholders find sufficiently reliable that they can use it as the basis for making decisions. Early in a project, this may mean that the plan says that the product can be released in the third quarter, rather than the second, and that it will contain approximately a described set of features. Later in the project, to remain useful for decision making, this plan will need to be more precise.
Suppose you are estimating and planning a new release of the company’s flagship product. You determine that the new version will be ready for release in six months. You create a plan that describes a set of features that are certain to be in the new version and another set of features that may or may not be included, depending on how well things progress.
Others in the company can use this plan to make decisions. They can prepare marketing materials, schedule an advertising campaign, allocate resources to assist with upgrading key customers, and so on. This plan is useful—as long as it is somewhat predictive of what actually happens on the project. If development takes twelve months instead of the planned six, this was not a good plan.
However, if the project takes seven months instead of six, the plan was probably still useful. Yes, the plan was incorrect, and yes, it may have led to some slightly mistimed decisions. But a seven-month delivery of an estimated six-month project is generally not the end of the world and is certainly within the PMI’s margin of error for a budgetary estimate. The plan, although inaccurate, was even more likely useful if we consider that it should have been updated regularly throughout the course of the project. In that case, the one-month late delivery should not have been a last-minute surprise to anyone.