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Here are four keys to accurately estimating task duration for projects. The use of these varies from project to project and on each project type but nonetheless these four keys will provide a high degree of confidence that your risk is limited as to duration of tasks.

The Four Keys

These four keys are:

1. Use subject matter experts “SME” for estimating each individual task.
2. Use tried and true techniques to provide checks against each other and provide a well rounded view of the potential task duration.
3. Allow for a reserve in your estimate to provide some level of padding in case of unknowns.
4. Provide your estimate in ranges.

Combining these four keys as part of your activity duration estimating process will give you confidence that you have thoroughly looked at all aspects concerning project task duration.

Three Estimating Techniques

One of the keys involves using estimating techniques. Here are three basic techniques that are helpful on most projects that do not require more sophisticated statistical techniques:

1. Analogous Estimating: as the word Analogous implies analogous estimating is all about finding similar task from past projects and trying to derive a consensus estimate based upon that past experience.
2. Parametric Estimating: is more about black and white, mathematical application. It is about knowing how long it might take to do a specific piece of the work extrapolating that out over the whole task and adding it out to arrive at a total estimate for the task.
3. Three Point Estimating: involves picking three points; An Optimistic Estimate, a Pessimistic Estimate and a “What do you really think it is going to take” estimate. These three points can provide a basis for an educated “Wag” at the estimate.

Application on Various types of Projects

These three techniques can be used in varied degrees depending on the project. For example, on a construction project the technology skill in subject matter experts tend to be well established. When estimating how long it might take to install drywall in a building, there are well established parameters allowing for effective parametric estimating. Analogous estimating is also helpful but most likely in the construction arena the parametric estimating can be very effective.

In the information technology world however, when estimating time duration for application development task, it is a whole different story. Often the difference in expertise of those doing the tasks can vary substantially. In addition, the technology is changing rapidly so it is not a controlled variable. Therefore, parametric estimating is less likely to be so accurate in estimating task for an application development project. Three point estimating combined with analogous estimating would tend to lend itself more to these types of projects.

Use the Four Keys for Better Estimating

It is good to have techniques as they help you to structure your activities and produce an ability to come up with a range of estimates to think about. For a project manager it is important to develop a strong sense for when you are confident in the estimates and when you feel there is a high deal of risk or variability involved.

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John Reiling, PMP

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