Any plan is based on estimates of time and resources needed to complete an activity. The accuracy of those estimates depends quite simply on the extent to which you have done something similar before. Where you are getting into activities that are outside the skills and experience of the project team, the accuracy of the estimates decreases and the level of risk involved increases.
Adopting the sliding planning window approach means that your estimates should become increasingly accurate as the project progresses. It is important that all members of the team understand the need for estimation in the project plan. If they fail to do so then they could become demoralised – viewing inaccurate estimation as failure. Where estimates are wrong the team needs to discuss the reasons for this in a positive manner so that all members of the team can contribute to increasing the accuracy of future estimates.
You need to be aware of the three possible responses you might get when asking someone how long it will take to do something:
- Padding – where individuals try to give themselves extra time by inflating the estimated duration to ensure they can complete the task “on time” e.g. they think it will take one week, they tell you it will take two weeks.
- Accurate – where individuals give an honest appraisal of how long they think the task will take.
- Squeezing – where individuals either want to curry favour or are frightened you won’t like the truth so they reduce the estimate to a level they are almost certain to fail to complete on time.
Not only can this mean that estimates are unrealistic but you can never be certain (unless you know the person’s likely approach) which of the three options they have chosen to use. When asking people to give an estimate, ask them to give three figures: their most optimistic, their most likely and their most pessimistic estimates. In this way you will get all three figures from everyone.
You must also be careful to ask the right question. There is a lot of difference between the two questions:
- How long will it take to write a twenty-page guide?
- How long, given everything else you have to do, will it take you to write a twenty-page guide?
Some people, if asked the first question would ignore anything else they may have to do, including their two-week annual leave that starts tomorrow, to answer the question assuming no interruptions whatsoever.