Before we get into the details of estimating, let’s make sure we are clear on where estimating falls in the schedule development and planning process. If someone stopped you on the street and asked you for an estimate, what is the minimum information that you would need? You would need to know what the estimate is for—what work is to be done. And you would need to know who is going to do it—what type of resources will be involved in performing the work. This flow is shown in Figure 7.1. Estimating the work should occur after you have identified the work and after you have thought about what resources are needed for the project.
It sounds so simple, doesn’t it? Then why is this so tough? These two basic prerequisites are where most estimating woes originate. There is often not a clear or complete understanding of the work to be performed by the person doing the estimate, and the relationship between the work estimate and the resource doing the work is not defined or communicated. In addition, there is the challenge of estimating work that has not been done before in exactly these conditions.
Yet, estimating the work effort is a cornerstone activity for planning the project. From these work estimates, we determine the project costs develop the project schedule (“Developing the Project Schedule”), and identify key project risks. This relationship is illustrated in Figure 7.2.
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