Ten Samples of Size Four Were Taken from a Process

Essay

Ten samples of size four were taken from a process, and their weights measured. The sample averages and sample ranges are in the following table. Construct and plot an x-bar and R-chart using this data. Is the process in control?
$$\begin{array} { | l | r | r | } \hline \text { Sample } & \text { Mean } & \text { Range } \\\hline 1 & 20.01 & 0.45 \\\hline 2 & 19.98 & 0.67 \\\hline 3 & 20.25 & 0.30 \\\hline 4 & 19.90 & 0.30 \\\hline 5 & 20.35 & 0.36 \\\hline 6 & 19.23 & 0.49 \\\hline 7 & 20.01 & 0.53 \\\hline 8 & 19.98 & 0.40 \\\hline 9 & 20.56 & 0.95 \\\hline 10 & 19.97 & 0.79 \\\hline\end{array}$$