In establishing control charts for a process, it is often essential to use both the x-bar chart and the R chart. Which of the following statements explain what these charts show?

Group of answer choices

The x-bar_ chart tells us the behavior of sample mean and the R chart tells us whether or not the x-bar chart is within control.

The R chart tells us the behavior of sample variability and the x bar chart tells us whether or not the R chart is within control.

The x bar chart tells us the behavior of sample mean and the R chart tells us the behavior of sample variability.

The R chart is an alternative approach to measure the number of defective units in a process.

None of the above statements is an acceptable explanation.