标题: 质量控制的工具和技术[Tools and Techniques for Quality Control] [打印本页] 作者: windows98 时间: 2008-12-29 08:47 标题: 质量控制的工具和技术[Tools and Techniques for Quality Control] .1 Inspection. Inspection includes activities such as measuring, examining, and testing undertaken to determine whether results conform to requirements. Inspections may be conducted at any level (e.g., the results of a single activity may be inspected, or the final product of the project may be inspected). Inspections are variously called reviews, product reviews, audits, and walkthroughs; 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. .5 Flowcharting. Flowcharting is described in Section 8.1.2.3. Flowcharting is used in quality control to help analyze how problems occur. .6 Trend analysis. Trend analysis involves using mathematical techniques to forecast future outcomes based on historical results. Trend analysis is often used to monitor: ◆ Technical performance—how many errors or defects have been identified,how many remain uncorrected. ◆ Cost and schedule performance—how many activities per period were completed with significant variances.