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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Xbar and R chart ： ウィキペディア英語版 Xbar and R chart | meanlimits = $\backslash bar\; x\; \backslash pm\; A\_2\; \backslash bar\; R$ | meanstatistic = $\backslash bar\; x\_i\; =\; \backslash frac\; \}$ }} In statistical quality control, the $\backslash bar\; x$ and R chart is a type of control chart used to monitor variables data when samples are collected at regular intervals from a business or industrial process. The chart is advantageous in the following situations: #The sample size is relatively small (say, n ≤ 10—$\backslash bar\; x$ and s charts are typically used for larger sample sizes) #The sample size is constant #Humans must perform the calculations for the chart The "chart" actually consists of a pair of charts: One to monitor the process standard deviation (as approximated by the sample moving range) and another to monitor the process mean, as is done with the $\backslash bar\; x$ and s and individuals control charts. The $\backslash bar\; x$ and R chart plots the mean value for the quality characteristic across all units in the sample, $\backslash bar\; x\_i$, plus the range of the quality characteristic across all units in the sample as follows: :R = xmax - xmin. The normal distribution is the basis for the charts and requires the following assumptions: *The quality characteristic to be monitored is adequately modeled by a normally distributed random variable *The parameters μ and σ for the random variable are the same for each unit and each unit is independent of its predecessors or successors *The inspection procedure is same for each sample and is carried out consistently from sample to sample The control limits for this chart type are: *$D\_3\; \backslash bar\; R$ (lower) and $D\_4\; \backslash bar\; R$ (upper) for monitoring the process variability *$\backslash bar\; x\; \backslash pm\; A\_2\; \backslash bar\; R$ for monitoring the process mean :where $\backslash bar\; x$ and $\backslash bar\; R\; =\; \backslash frac\; -\; R\_\; \backslash right\; )\}$ are the estimates of the long-term process mean and range established during control-chart setup and A2, D3, and D4 are sample size-specific anti-biasing constants. The anti-biasing constants are typically found in the appendices of textbooks on statistical process control. As with the $\backslash bar\; x$ and s and individuals control charts, the $\backslash bar\; x$ chart is only valid if the within-sample variability is constant. Thus, the R chart is examined before the $\backslash bar\; x$ chart; if the R chart indicates the sample variability is in statistical control, then the $\backslash bar\; x$ chart is examined to determine if the sample mean is also in statistical control. If on the other hand, the sample variability is ''not'' in statistical control, then the entire process is judged to be not in statistical control regardless of what the $\backslash bar\; x$ chart indicates. ==See also== *$\backslash bar\; x$ and s chart *Shewhart individuals control chart 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「Xbar and R chart」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.