Estimating Task Duration Describe the Various Methods

Estimating Task Duration

Describe the various methods for estimating task duration and discuss how these methods improve the accuracy of task duration estimates, taking into account the variation that is present in task duration. Provide practical examples to help illustrate the differences between the methods.

There are basically six methods of estimating task duration which are: similarity to other activities, historical data, expert advice, Delphi technique, Three-point technique, and Wide-band Delphi technique (Franchina, 2010). The similarity to other activities is pretty straight forward and this is where the project activity duration is similar to an activity that has been perform and documented. Having completed a similar activity already, the previous task can provide many insights into cost and duration of repeating the activity. If the same task has not been performed internally then the project can look at historical data from a range of different sources to estimate the duration.

Individuals who have performed similar activities before it is a powerful way to obtain realistic and achievable estimates as the individual's knowledge, skills and experience that they have gained will improve the accuracy of such estimates (PMP Primer, N.d.). Experts that have significant experience performing similar activities can quickly get a feel for the resources and activity durations that will be required to complete a project task. However, the level of expertise must be present or the estimates could be subject to inaccuracies.

Figure 1 - Activity Estimation (PMP Primer, N.d.)

The Delphi technique and the wide-band version all involve expert opinion. However, more than one expert is considered as opposed to expert estimation. This allows the estimate to eliminate a level of biasness. Usually, one or more of the following properties of the application leads to the need for employing Delphi (Linstone & Turoff, 2002):

The problem does not lend itself to precise analytical techniques but cart benefit from subjective judgments on a collective basis

The individuals needed to contribute to the examination of a broad or complex problem have no history of adequate communication and may represent diverse backgrounds with respect to experience or expertise

More individuals are needed than can effectively interact in a face-to-face exchange

Time and cost make frequent group meetings infeasible

The efficiency of face-to-face meetings can be increased by a supplemental group communication process

Disagreements among individuals are so severe or politically unpalatable that the communication process must be refereed and/or anonymity assured

The heterogeneity of the participants must be preserved to assure validity of the results, i.e., avoidance of domination by quantity or by strength of personality ("bandwagon effect")