Which of the following is not found on an x bar and R control chart?

The capability ratio is not found on an x bar and R control chart because this type of chart is specifically designed to monitor the stability and performance of a process over time through its average and range. The x bar chart tracks the process average by displaying the mean of samples over time, while the R chart monitors the variability or range within those samples.

Control limits are crucial components of these charts, as they define the upper and lower expectations for process performance under normal operating conditions. Additionally, the sample size is an integral part of the charts as they depend on the number of observations used to calculate the averages and ranges. The capability ratio, however, is related to determining how well a process meets specified limits relative to its inherent variability, but such information is not included in the construction or interpretation of x bar and R charts themselves. Thus, the capability ratio is more relevant in assessing process capability rather than ongoing process control, making it absent from x bar and R control charts.