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. Wysocki (2009, P149) indicates that there are “Six Methods for Estimating Task Duration”, these are 1. Similarity to other activities
2. Historical Data
3. Exert Advice
4. Delphi Technique
5. Three Point Technique
6. Wide-band Delphi Technique
(Wysocki 2009, p.149)
Before the overall project duration can be estimated in must first be broken down into manageable smaller activities, the series of tasks generated, once identified and organized into a logical sequence this forms the basis of the Project Work Breakdown Structure (WBS). Once the WBS is built the activities can be assigned durations based on the various estimating methods to develop the overall project plan. 1. Similarity to other activities.
If the task is something simple and/or a repetitive task that has been done in previous projects on numerous occasions it is safe to say that the durations taken previously could be used again. Whilst this is probably the most simple approach other considerations must also be looked at, for example there is no point in estimating that a taxi duration from the city centre in Jakarta to the airport will take 30minutes because that is what it took the last time. The environment, time of day, weather conditions and many other considerations must be factored in to ensure the time in realistic. 2. Studying Historical Data.
If in a project we had to plan for many taxi trips to the airport as mentioned above perhaps considering the historical data of durations would give us a better average time. So in the last year I have made 12 trips to the airport (1 a month) and at various times of the day and night, the durations have varied from 30mins to 3hrs thus for...
References: Robert K. Wysocki, Effective Project Management, John Wiley & Sons (P&T) p. 149
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