Use the data shown to set up an $\stackrel{}{x}$ and $R$ control chart that plots products A and $B$ on

the same control chart. It is assumed that the standard deviation is the same for both

product types. The nominal dimensions of A and B are $25$ and $80$ respectively.

i$)$ Setup and plot a suitable $\stackrel{}{x}$ and $R$ control chart for this process.

ii$)$ Is the process in statistical control? Explain your answer.

iii$)$ If the standard deviations of both products were different, what changes to the

control chart would have had to make in order to plot both products on the same

control chart.