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Unformatted text preview: in some application areas, these terms have narrow and specific meanings. .2 Control charts. Control charts are a graphic display of the results, over time, of a process. They are used to determine if the process is "in control" (e.g., are differences in the results created by random variations, or are unusual events occurring whose causes must be identified and corrected?). When a process is in control, the process should not be adjusted. The process may be changed to provide improvements, but it should not be adjusted when it is in control. Control charts may be used to monitor any type of output variable. Although used most frequently to track repetitive activities, such as manufactured lots, control charts can also be used to monitor cost and schedule variances, volume and frequency of scope changes, errors in project documents, or other management results to help determine if the project management process is in control. Figure 8-4 is a control chart of project schedule performance. .3 Pareto diagrams. A Pareto diagram is a histogram, ordered by frequency of occurrence, that shows how many results were generated by type or category of identified cause (see Figure 8-5). Rank ordering is used to guide corrective action--the project team should take action to fix the problems that are causing the greatest number of defects first. Pareto diagrams are conceptually related to Pareto's Law, which holds that a relatively small number of causes will typically produce a large majority of the problems or defects. This is commonly referred to as the 80/20 principle, where 80 percent of the problems are due to 20 percent of the causes. .4 Statistical sampling. Statistical sampling involves choosing part of a population of interest for inspection (e.g., selecting ten engineering drawings at random from a list of seventy-five). Appropriate sampling can often reduce the cost of quality control. There is a substantial body of knowledge on statistical sampling; in some application areas, it is necessary for the project management team to be familiar with a variety of sampling techniques. 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 103 ACROYMNS LIST Chapter 8--Project Quality Management Figure 84 | Figure 85 Upper Control Limit X Lower Control Limit The x axis of all control charts consists of sample numbers (usually the time of the sample). Control charts have three common lines: I. A center line, designated with an "x," which provides the average (x) of the process data. II. An upper line designating the upper control limit (UCL), drawn at a calculated distance above the center line, showing the upper range of data. III. The lower line designating the lowe...
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This document was uploaded on 09/27/2013.
- Fall '13
- The American