The truncated distribution a smooth curve with an

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The truncated distribution (a smooth curve with an abrupt ending on one side): This is often caused by external forces to the process, such as screening, 100% inspection, or a review process. Since truncating unusually indicates added costs, it is a good candidate for improvement. The isolated peak distribution (a small, separate, group of data to one side of the parent group): Look for poor inspection, measurement errors or data entry errors. Edge-peaked distribution (a peak right at the edge): This usually means that data from an otherwise long tail have been lumped together at one point (data from outside the limit have been recorded as being inside the limit). 2.7.4 Pareto Analysis It uses a specially organised histogram (the Pareto chart) to provide a picture that instantly identifies those problems of the greatest concern, those problems that should be addressed first. 2.7.5 Cause and Effect Diagram As the name implies, this tool is just a group of causes and effects diagrammed to show the interrelationships. The diagram is a form of tree diagram on its side so that it looks like a fishbone. The name Ishikawa refers to the Japanese man who conceived the chart. The diagram is formed by first stating the problem in the form of an effect. In fig. 2.7, the problem is to maximise hardness, within limits. Hardness, then, is the main effect. The main causes are then placed at the end of the lines extending up and down at an angle from the centre line. These main causes are usually some form of the following manufacturing factors like materials, equipment, work methods, operators/workers, processes, tooling, management (policies), measurement, environment, etc. the first three usually account for 80% of all problems. Each of these main causes is now treated as effects and causes determined for each of them, and then each of the secondary causes is treated as effects and causes found for each of them, and so on. The procedure is continued until all causes are identified.
45/ ADTU OLE Machine A Operator A Machine B Loader METHODS PROCESS OPERATOR MEASUREMENT TOOLING MATERIAL Material RM2 Part P4 Hardness Fig. 2.7 Basic cause and effect diagram Each cause, no matter where placed on the chart, must relate to the main effect. If the chart is complex and extensive, secondary charts can be constructed from any of the causes. That cause then becomes the main effect of the secondary charts can be constructed from any of the causes. That cause then becomes the main effect of the secondary chart. The causes and effects are best determined by forming a team of those most concerned with the main problem, and then using a team of storming procedure. Any quality characteristic can become an effect around which a cause and effect chart is constructed. However, if the problem is people, consider using a desired result rather than a problem as the main effect. In other words, concentrate on the desired characteristics rather than how to change people. Cause and effect diagrams

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