质量控制的工具和技术[Tools and Techniques for Quality Control]

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.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.

1． 检查：检查包括测量、检查和测试等活动，目的是确定项目成果是否与要求相一致。检查可以在任何管理层次中开展（例如，一个单项活动的结果和整个项目的最后成果都可以检验）。检验有各种名称：审查、产品审查、审计及巡回检查。在一些应用领域中，这些词汇有狭义和特定的专门含义。

2． 控制图：控制图是根据时间推移对过程运行结果的一种图表展示。常用于判断过程是否"在控制中"进行（例如，过程运行结果中的偏差是因随机变化所产生？还是异常事件引发的？若是异常事件引发的就必须对异常事件的原因查清并纠正）。当一个过程在控制之中时，不应对它进行调整。这个过程可能为了得到改进而有所变动，但只要它在控制范围之中，就不应人为地去调整它。 控制图可以用来监控各种类型的变量的输出。尽管控制图常被用于跟踪诸如批量加工等重复性的活动，它还可以用于监控成本和进度计划的偏差、范围变更的幅度和频率、项目文件中的错误，或者其他管理结果，以便帮助确定"项目管理过程"是否在控制之中。图8-4 即为项目进度计划绩效的控制图。  

3． 帕累托图：是一种直方图，按事件发生的频率排序而成，用以显示已确定的各种类型的原因产生结果的数量（见图8-5）。等级序列是用来指导纠错行动的--项目团队应采取措施首先去解决导致最多缺陷的问题。帕累托图与帕累托定律有关。此定律认为绝大多数的问题或缺陷产生于相对有限的起因。这就是常说的80/20 定律，即20% 的原因造成80% 的问题。

4．统计抽样：抽取总体中的一个部分进行检验（例如，从一份包括75 张设计图纸的清单中随机抽取10 张）。适当的抽样调查往往能降低质量控制成本。关于抽样调查统计有大量书面资料和知识体系。在一些应用领域，熟悉各种抽样调查技术对于项目管理团队是十分必要的。

5． 流程图：见8.1.2.3 部分。质量控制中运用流程图有助于分析问题是如何发生的。

6． 趋势分析：趋势分析是根据历史结果，利用数学技术预测未来的成果。趋势分析常用来监测： z 技术绩效--有多少错误和缺陷已被指出，有多少仍未纠正。 z 成本和进度绩效--每个阶段完成了多少有重大偏差的活动。

gerry

Goog translation. Excellent!

Study

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wy20030212

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闭月羞云

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时光倒流

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facekiss

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烟的寂寞

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时光倒流

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流星

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