Estimating

With a good draft of the WBS, the project manager estimates the effort required to complete each of the lower level items in the work breakdown structure. Often, estimating is highly subjective, reflecting extreme optimism or pessimism. Rarely do estimates emerge realistic. To overcome the effects of extreme optimism or pessimism, a formula — called the three-point estimate technique — exists to compensate for the tendency towards exaggeration. For each low level item, the project manager looks at three variables: most optimistic, most pessimistic, and most likely. The most pessimistic is the time required to complete a task under the worst conditions. The most optimistic is the time under the best conditions. The most likely is the time under "typical" or "normal" conditions. Next, the variables are plugged into a formula:

Expected Time = Most Pessimistic + 4(Most Likely) + Most Optimistic / 6 Example: 120 hours + 4(80 hours) + 60 / 6 = 83.33 hours

After estimating, the project manager translates the figures into flow, or work, days to develop schedules. The time is typically divided into units of eight hours.