Six Methods for the Estimation of Activity Duration in Project Management

Having a accurate estimate of the activity duration greatly aids you in planning for the whole project
Having a accurate estimate of the activity duration greatly aids you in planning for the whole project (Image: Jupiterimages/Comstock/Getty Images)

A project is a temporary organization that is required to create a unique and predetermined outcome at a predetermined time by means of predetermined resources. Project management is the use of information and techniques to accomplish a given project effectively and efficiently. Project management helps to minimize failure, manage time schedules, and keep expenses and resources close to the budget.

Analogous Estimation

It requires you to analyze previous projects to approximate the length of the activity. It depends on selecting a completed project or sections of it, similar to the new project, and using the definite time from the finished project to estimate duration of the new project.

Expert Judgment

This is one of the most frequently used methods for estimating the duration of activities in projects. Experts, project leaders, and project consultants who have performed similar projects in the previously can provide you with expert judgment.

Three-Point Estimates

This method makes use of three estimates: 1) most likely 2) optimistic and 2) pessimistic to estimate activity duration. Additionally, you can use it to improve the accuracy of the activity-duration estimate. An optimistic estimate refers to the shortest time; pessimistic to the longest time, while "most likely" is the normal time taken. This method uses past data to arrive at these estimates.

Parametric Estimation

Parametric estimating uses the statistical correlation that exists between a set of historical data and a series of delineated list of other variables. Use this information for the purposes of calculating an estimate for activity duration. One important feature of parametric estimating: it provides higher levels of accuracy (providing your original data for estimating was also accurate).

The Delphi Technique

Inquire from several independent experts to estimate the duration of an activity in a project and then evaluate the results to provide an objective estimate. The method is based on the assumption that the independent experts are unknown to each other and thus their individual biases will cancel out resulting in an accurate estimate (Ref 4).

Wideband Delphi Technique

Collect information from a set of experts separately, share these results, and inquire from the experts their opinion again based on now knowing the opinions of others. Discuss assumptions made by individual experts where there are large disparities. As the group progresses through rounds, sharing their knowledge and assumptions, duration estimations among the experts become increasingly alike and this results in a consensus (Ref 5).

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