From the course: Project Management Foundations: Schedules

Methods for estimating activities - Microsoft Project Tutorial

From the course: Project Management Foundations: Schedules

Methods for estimating activities

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- There are many methods for estimating duration and work. The best one for each project depends on the project, your organization's methodology, available historical data, and resources. If you have information about a similar project in the past or team members' performance on other projects, incorporate that data. Estimating based on previous actual results is a great way to get an accurate estimate. Another method is to ask people who understand the work to estimate it. For example, give team members the big picture of the project and describe the activities. Have them estimate how long it would take them to complete the work. Another option is to ask experts, like senior employees or external consultants. There are two sensible actions to take when you get estimates from others. One, you can trust that the estimates are good. Or two, if you have your doubts, get a second opinion. Expanding on the concept of second opinions is an estimating technique called the Delphi Method. It's based on the idea that more heads are better than one. You can ask several experts to estimate independently. You share the results with the group and ask them to re-estimate. Repeat this step of sharing and re-estimating a couple more times, and then use the average of the last round as your final estimated value. Sometimes people share the reasoning the experts give for their estimates. Others simply share the estimate values. Interestingly, the Delphi Method seems to produce good estimates either way, so use the approach you prefer. Let's walk through an example of the Delphi Method. In the first round, one estimator comes in on the high end with 10 days. Another estimator is on the low end with four days. And the third estimator estimates seven days. In the second round, the high estimate comes down to nine days. The other two increase their estimates. Maybe they thought of some work they forgot. The third round high and low estimates continue to move toward the middle while estimator three sticks with her second round number. The estimates in the fourth round seem to stabilize, so we'll use the average of this round as the estimate. Add the three estimates together and divide by three to get 7.7 days. We'll round up to eight days. Another approach is PERT, which stands for Program Evaluation and Review Technique. You ask people to produce optimistic, pessimistic, and most likely estimates. For example, the optimistic estimate for a task is four days. The pessimistic estimate is 10 days. The most likely estimate is six days. The weighted average of these estimates comes out to be 6.33 days. The PERT method uses these estimates to run multiple simulations of the project to determine possible outcomes. With statistical analysis, you can determine the probability of the project finishing within a specific timeframe. PERT is a good choice when a project is unfamiliar or carries a lot of uncertainty. It makes people think about risks and it emphasizes the uncertain nature of estimates. These are just a few ways to estimate activities. There may be other methods specific to your industry. Ask your colleagues for approaches they recommend.

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