A Manufacturer of Dustless Chalk Instituted a Quality Control Program

Essay

A manufacturer of dustless chalk instituted a quality control program to monitor chalk density. The sample standard deviations of densities of n = 8 chalk specimens, were as follow: $$\begin{array} { l l l l l l l l } .165 & .231 & .073 & .165 & .292 & .371 & .179 & .234 \\.408 & .207 & .170 & .249 & .296 & .138 & .111 & .076 \\.224 & .335 & .116 & .204 & .250 & .232 & .342 & .307\end{array}$$ Calculate limits for an S chart, and check for out-of-control points. If there is an out-of-control point, delete it and repeat the process.