Samples
Twenty-Five Samples of Size 4 Were Taken from a Production

Samples
Twenty-five samples of size 4 were taken from a production process.The mean of the sample means is $\bar {\bar x}$ = 13.9.The process standard deviation is known to be $\sigma$ = 3.5.The sample means are listed below. $$\begin{array}{l}\begin{array} { | c | c c c c c c c c c c c c c | } \hline \text { Sample } & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11 & 12 & 13 \\\hline \bar { x } _ { j } & 15.1 & 10.9 & 17.6 & 10.0 & 13.8 & 9.9 & 17.7 & 6.1 & 5.9 & 16.9 & 11.1 & 12.1 & 9.4 \\\hline\end{array}\\\\\begin{array} { | c | c c c c c c c c c c c c | } \hline \text { Sample } & 14 & 15 & 16 & 17 & 18 & 19 & 20 & 21 & 22 & 23 & 24 & 25 \\\hline \bar { x } _ { j } & 13.2 & 11.1 & 16.9 & 9.3 & 10.0 & 12.0 & 18.2 & 21.1 & 21.7 & 16.9 & 19.1 & 21.5 \\\hline\end{array}\end{array}$$
-Is the process under control? Discuss.