$3-$

Specifications on a normally distributed dimension are $600+-20.\stackrel{}{x}$ and $R$ charts are maintained on this

dimension and have been in control over a long period of time. The parameters of these control charts are as

follows $(n=9).$

$($a$)$ What are your conclusions regarding the capability of the process to produce items within specifications?

$($b$)$ Construct an OC curve for the $\stackrel{}{x}$ chart assuming that $$ is constant.