Np-chart

{{Infobox control chart | name = np-chart | proposer = Walter A. Shewhart | subgroupsize = n > 1 | measurementtype = Number nonconforming per unit | qualitycharacteristictype = Attributes data | distribution = Binomial distribution | sizeofshift = ≥ 1.5σ | meanchart = Np control chart.svg | meancenter = n \bar p = \frac {\sum_{i=1}^m \sum_{j=1}^n \begin{cases} 1 & \mbox{if }x_{ij}\mbox{ defective} \\ 0 & \mbox{otherwise} \end{cases}}{m} | meanlimits = n \bar p \pm 3\sqrt{n \bar p(1- \bar p)} | meanstatistic = n \bar p_i = \sum_{j=1}^n \begin{cases} 1 & \mbox{if }x_{ij}\mbox{ defective} \\ 0 & \mbox{otherwise} \end{cases} }} In statistical quality control, the np-chart is a type of control chart used to monitor the number of nonconforming units in a sample. It is an adaptation of the p-chart and used in situations where personnel find it easier to interpret process performance in terms of concrete numbers of units rather than the somewhat more abstract proportion. The np-chart differs from the p-chart in only the three following aspects: #The control limits are n\bar p \pm 3\sqrt{n\bar p(1-\bar p)} , where n is the sample size and \bar p is the estimate of the long-term process mean established during control-chart setup. #The number nonconforming (np), rather than the fraction nonconforming (p), is plotted against the control limits. #The sample size, n , is constant.

{{Infobox control chart | name = np-chart | proposer = Walter A. Shewhart | subgroupsize = n > 1 | measurementtype = Number nonconforming per unit | qualitycharacteristictype = Attributes data | distribution = Binomial distribution | sizeofshift = ≥ 1.5σ | meanchart = Np control chart.svg | meancenter = n \bar p = \frac {\sum_{i=1}^m \sum_{j=1}^n \begin{cases} 1 & \mbox{if }x_{ij}\mbox{ defective} \\ 0 & \mbox{otherwise} \end{cases}}{m} | meanlimits = n \bar p \pm 3\sqrt{n \bar p(1- \bar p)} | meanstatistic = n \bar p_i = \sum_{j=1}^n \begin{cases} 1 & \mbox{if }x_{ij}\mbox{ defective} \\ 0 & \mbox{otherwise} \end{cases} }} In statistical quality control, the np-chart is a type of control chart used to monitor the number of nonconforming units in a sample. It is an adaptation of the p-chart and used in situations where personnel find it easier to interpret process performance in terms of concrete numbers of units rather than the somewhat more abstract proportion. The np-chart differs from the p-chart in only the three following aspects: The control limits are n\bar p \pm 3\sqrt{n\bar p(1-\bar p)} , where n is the sample size and \bar p is the estimate of the long-term process mean established during control-chart setup. The number nonconforming (np), rather than the fraction nonconforming (p), is plotted against the control limits. The sample size, n , is constant.

See also

p-chart

References

Text derived from https://en.wikipedia.org/w/index.php?oldid=918895813 under CC BY-SA 4.0; modifications have been made.