Refer to Exercise 12.28 as it relates to the 20 preliminary subgroups on percents of aluminum content. The acceptable range for the percents of aluminum is 3.8% to 4.2%.
alloy
Obtain the individual observations and make a Normal quantile plot of them. What do you conclude? (If your software will not make a Normal quantile plot, use a histogram to assess Normality.)
Estimate .
Estimate .
Comparing your results from parts (b) and (c), what would you recommend to improve process capability?