Four samples $($kequals$4)$ are taken from a$$ process, with each sample consisting of five observations $($nequals$5).$ The sampled items are subjected to a stress$$ test, and the amount of$$ pressure, measured in pounds per square$$ inch, required to crack each item was computed. The results are shown below. Develop an R Chart to determine if the dispersion is stable or not.

LOADING... Click the icon to view the samples data.

LOADING... Click the icon to view the values of the Upper D $3$ and Upper D $4$ constants.

Part $2$

The average of the sample ranges is