Unformatted text preview: 6-4). PERT itself is seldom used today. .2 Duration compression. Duration compression is a special case of mathematical analysis that looks for ways to shorten the project schedule without changing the project scope (e.g., to meet imposed dates or other schedule objectives). Duration compression includes techniques such as: Crashing--in which cost and schedule tradeoffs are analyzed to determine how, if at all, to obtain the greatest amount of compression for the least incremental cost. Crashing does not always produce a viable alternative and often results in increased cost. Fast tracking--doing activities in parallel that would normally be done in sequence (e.g., starting to write code on a software project before the design is complete, or starting to build the foundation for a petroleum processing plant before the 25 percent engineering point is reached). Fast tracking often results in rework and usually increases risk. .3 Simulation. Simulation involves calculating multiple project durations with different sets of activity assumptions. The most common technique is Monte Carlo Analysis, in which a distribution of probable results is defined for each activity and used to calculate a distribution of probable results for the total project (see also Section 18.104.22.168). In addition, what-if analyses can be made using the logic network to simulate different scenarios, such as delaying a major component delivery, extending specific engineering durations, or introducing external factors (such as a strike, or a change in the permitting process). The outcome of the what-if simulations can be used to assess the feasibility of the schedule under adverse conditions, and in preparing contingency/response plans to overcome or mitigate the impact of unexpected situations. A Guide to the A Guide to the Project Project Management Management Body of Body of KnowledgeE L KnowledgeE PL MP AM SA S A Guide to the Project Management Body of Knowledge (PMBOK Guide) 2000 Edition 2000 Project Management Institute, Four Campus Boulevard, Newtown Square, PA 19073-3299 USA NAVIGATION LINKS ACROYMNS LIST ACRONYMS LIST 75 ACROYMNS LIST Chapter 6--Project Time Management Figure 64 | 22.214.171.124 Higher Most Likely (used in original CPM calculations) Probability of Occurrence (
Optimistic PERT Weighted Average = Optimistic + 4 Most Likely + Pessimistic 6 ) Beta Distribution Pessimistic
Longer ment ment Lower Shorter Possible Durations
Figure 64. PERT Duration Calculation for a Single Activity geE L geE PL P .4 Resource leveling heuristics. Mathematical analysis often produces a preliminary early-start schedule that requires more resources during certain time periods than are available, or requires changes in resource levels that are not manageable. Heuristics, such as, "Allocate scarce resources to critical path activities first," can be applied to develop a schedule that reflects such constraints. Resource leveling often results in a project duration that is longer than the prel...
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