Cartons of Plaster of Paris Are Supposed to Weigh Exactly

Essay

Cartons of Plaster of Paris are supposed to weigh exactly 32 oz. Inspectors want to develop process control charts. They take ten samples of six boxes each and weigh them. Based on the following data, compute the lower and upper control limits and determine whether the process is in control.
$$\begin{array} { | c | c | c | } \hline \text { Sample } & \text { Mean } & \text { Range } \\\hline 1 & 33.8 & 1.1 \\\hline 2 & 34.6 & 0.3 \\\hline 3 & 34.7 & 0.4 \\\hline 4 & 34.1 & 0.7 \\\hline 5 & 34.2 & 0.3 \\\hline 6 & 34.3 & 0.4 \\\hline 7 & 33.9 & 0.5 \\\hline 8 & 34.1 & 0.8 \\\hline 9 & 34.2 & 0.4 \\\hline 10 & 34.4 & 0.3 \\\hline\end{array}$$