Xbar and R Chart (Paperback)

High Quality Content by WIKIPEDIA articles! In statistical quality control, the bar x and R chart is a type of control chart used to monitor a variables data when samples are collected at regular intervals from a business or industrial process. 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 bar x and s and individuals control charts. The bar x and R chart plots the mean value for the quality characteristic across all units in the sample, bar x_i, plus the standard deviation of the quality characteristic across all units in the sample.