# Calculating Expected Time Durations Using PERT-Representing and Scheduling Project Plans

Calculating Expected Time Durations Using PERT

One of the most difficult and most error-prone activities when constructing a project schedule is the determination of the time duration for each task within a work breakdown structure. It is particularly problematic to make these estimates when a high degree of complexity and uncertainty characterize a task. PERT (program evaluation review technique) is a technique that uses optimistic, pessimistic, and realistic time estimates to calculate the expected time for a particular task. This technique helps you obtain a better time estimate when you are uncertain as to how much time a task will require to be completed. The optimistic (o) and pessimistic ( p) times reflect the minimum and maximum possible periods of time for an activity to be completed. The realistic time (r), or most likely time, reflects the project manager’s “best guess” of the amount of time the activity will require for completion. Once each of these estimates is made for an activity, an expected completion time (ET) can be calculated for that activity. Because the expected completion time should be closer to the realistic time (r), the realistic time is typically weighted 4 times more than the optimistic (o) and pessimistic ( p) times. Once you add these values together, it must be divided by 6 to determine the ET. This equation is shown in the following formula:

For example, suppose that your instructor asked you to calculate an expected time for the completion of an upcoming programming assignment. For this assignment, you estimate an optimistic time of 2 hours, a pessimistic time of 8 hours, and a most likely time of 6 hours. Using PERT, the expected time for completing this assignment is 5.67 hours. Commercial project management software such as Microsoft Project assists you in using PERT to make expected time calculations. Additionally, many commercial tools allow you to customize the weighing of optimistic, pessimistic, and realistic completion times.

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## Frequently Asked Questions

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Ans: Project scheduling and management requires that time, costs, and resources be controlled. view more..
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Ans: A project manager has a wide variety of techniques available for depicting and documenting project plans. view more..
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Ans: The focus of project closedown is to bring the project to an end. Projects can conclude with a natural or unnatural termination. view more..
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Ans: One of the most difficult and most error-prone activities when constructing a project schedule is the determination of the time duration for each task within a work breakdown structure. view more..
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Ans: lthough Pine Valley Furniture has historically been a manufacturing company, it recently entered the direct sales market for selected target markets. view more..
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Ans: A wide variety of automated project management tools are available to help you manage a development project. view more..
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Ans: Defining the general project information includes obtaining the name of the project and project manager and the starting or ending date of the project. view more..
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Ans: A wide variety of automated project management tools are available to help you manage a development project. view more..
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Ans: Project identification and selection consists of three primary activities: identifying potential development projects, classifying and ranking projects, and selecting projects for development. Each of these activities is described next. view more..
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Ans: Many activities performed during initiation and planning could also be completed during the next phase of the SDLC—systems analysis. view more..
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Ans: Most information systems projects have budgets and deadlines. view more..
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Ans: All the information collected during project initiation and planning is collected and organized into a document called the baseline project plan. view more..
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Ans: Most businesses have discovered the power of Internet-based electronic commerce as a means to communicate efficiently with customers and to extend their marketing reach. view more..
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Ans: As stated earlier and shown in Figure 5-1, the two parts to systems analysis are determining requirements and structuring requirements. view more..
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Ans: Even though we called interviews, questionnaires, observation, and document analysis traditional methods for determining a system’s requirements, all of these methods are still used by analysts to collect important information. view more..
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Ans: Whether traditional or modern, the methods for determining system requirements that you have read about in this chapter apply to any requirements determination effort, regardless of its motivation. view more..
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Ans: In the last chapter, you read how Pine Valley Furniture’s management began the WebStore project—to sell furniture products over the Internet. view more..
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Ans: Collection of information is at the core of systems analysis. view more..

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