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Analogous Estimating Analogous estimating also known as top-down estimating is

a technique that uses actual durations from similar tasks on a previous project. This is
most frequently used at the early stages of project planning, when you have limited
information about the project. Although analogous estimating can provide a good
approximation of task duration, it is typically the least accurate means of obtaining an
estimate. No two projects are the same, and there is the risk that the project used to

obtain the analogous estimates is not as similar to the current project as it appears.
Results from analogous estimating are more accurate if the person doing the

estimating is familiar with both projects and is able to understand the differences that
could impact the activity durations on the new project.

Expert Judgment Expert judgment is a technique where the people most familiar
with the work determine the estimate. Ideally, the project team member who will
perform the task should provide the estimate. If all the team members haven’t been
identified yet, recruit people with expertise for the tasks you need estimated. Ask for

people who have completed a similar task on a previous project to assist with the
estimates for this project.

Remember that people with more experience will likely provide a shorter estimate for
an activity than someone who doesn’t have as much experience. You should validate
the estimate or ask other experts in the department to validate it for you.

Parametric Estimating Parametric estimating is a quantitatively based estimating
method that multiplies the quantity of work by the rate. To apply quantitatively based

durations, you must know the productivity rate of the resource performing the task or
have a company or industry standard that can be applied to the task in question. The
duration is obtained by multiplying the unit of work produced by the productivity rate.
For example, if a typical cable crew can bury 5 miles of cable in a day, it should take 10
days to bury 50 miles of cable.

PERT The Program Evaluation and Review Technique (PERT) is a method that the
U.S. Navy developed in the 1950s. The Navy was working on one of the most complex

engineering projects in history at the time—the Polaris Missile Program—and needed a
way to manage the project and forecast the project schedule with a high degree of
reliability. PERT was developed to do just that.

PERT and three-point estimates are similar techniques. The difference is that three-
point estimates use an average estimate to determine project duration, while PERT
uses what’s called expected value (or the weighted average). Expected value is

calculated using the three-point estimates for activity duration and then finding the
weighted average of those estimates.

The formula to calculate expected value is as follows:

(optimistic + pessimistic + (4 × most likely)) / 6

Using the same numbers used in the three-point estimates produces the following

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