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| meanlimits = | meanstatistic = xi }} In statistical quality control, the individual/moving-range chart is a type of control chart used to monitor variables data from a business or industrial process for which it is impractical to use rational subgroups. The chart is necessary in the following situations: #Where automation allows inspection of each unit, so rational subgrouping has less benefit. #Where production is slow so that waiting for enough samples to make a rational subgroup unacceptably delays monitoring #For processes that produce homogeneous batches (e.g., chemical) where repeat measurements vary primarily because of measurement error The "chart" actually consists of a pair of charts: one, the individuals chart, displays the individual measured values; the other, the moving range chart, displays the difference from one point to the next. As with other control charts, these two charts enable the user to monitor a process for shifts in the process that alter the mean or variance of the measured statistic. ==Interpretation== As with other control charts, the individuals and moving range charts consist of points plotted with the control limits, or natural process limits. These limits reflect what the process will deliver without fundamental changes. Points outside of these control limits are signals indicating that the process is not operating as consistently as possible; that some assignable cause has resulted in a change in the process. Similarly, runs of points on one side of the average line should also be interpreted as a signal of some change in the process. When such signals exist, action should be taken to identify and eliminate them. When no such signals are present, no changes to the process control variables (i.e. "tampering") are necessary or desirable.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Shewhart individuals control chart」の詳細全文を読む スポンサード リンク
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