What Is an Estimate?
WWPMM defines an estimate as an assessment of the likely quantitative result based on experience or historical data from previous projects, if any.
You will usually estimate the number of labor hours, labor costs, and other costs (material, travel, and so on.) for the project. The following terms are a key part of estimating and are used throughout this module:
- Effort is the number of labor units required to complete a task. It is usually measured in staff hours, or person-hours. When you think of effort, think of how much labor has to be used on the project. This is normally the first thing that you will estimate on a project.
- Duration is the number of work periods, excluding holidays or other nonworking periods, required to complete an activity or other project element. When you think of duration, think of how much time elapses. Later you will learn how to convert effort into duration.
- Levels of effort (LOE) activities support projects but are not specifically put into the schedule. For example, you might determine that you will need a half-time administrative person to support the project. You will not list every activity this person will do in the schedule, but you know you need this person’s time throughout the project.
An estimate should ideally include some indication of accuracy. Early in the project planning, you won’t know all the details about the project, and so your estimates will have a wide accuracy range around them, perhaps as much as 50% under to 100% over. But as you plan the project in detail, you should be able to produce estimates with a narrower range of accuracy, say 5% under to 10% over.