Control Limits for Xbar-R Chart

Hint: Use this chart to determine the Upper Control Limit (UCL) and Lower Control Limit (LCL) for a Xbar-R chart. Mean and Range (Xbar-R) chart is used when you have Continuous data with a Sample Size of less than eight

Grand Mean (x-bar-bar)
Calculate individual average of the observations for each time period. Then calculate the grand mean i.e average of averages
Average Range
Calculate range for each time period. Then calculate the average range i.e average of all ranges
Sample Size (between 2 and 8)
Upper Control Limit (UCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Lower Control Limit (LCL) for Sample Mean Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Range Chart
Upper Control Limit (UCL) for Sample Range Chart
Lower Control Limit (LCL) for Sample Range Chart
Lower Control Limit (LCL) for Sample Range Chart
Lower Control Limit (LCL) for Sample Range Chart
Control Limits Not Applicable
Control Limits cannot be calculated since a negative average range was entered. Enter a value greater than zero
Use Xbar-S Chart
Since the number of observations in each sub-group is greater than eight, it is recommended to use a Xbar-S chart
Use I-MR Chart
Since the number of observation in each sub-group is one, it is recommended to use an I-MR chart

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