=+22. The article “The Foreman’s View of Quality Control” (Quality Engr., 1990: 257–280) described an investigation into the coating weights for large pipes resulting from a galvanized coating process.

Production standards call for a true average weight of 200 lb per pipe. The accompanying descriptive summary and boxplot are from Minitab.

Variable N Mean Median TrMean StDev SEMean ctg wt 30 206.73 206.00 206.81 6.35 1.16 Variable Min Max Q1 Q3 ctg wt 193.00 218.00 202.75 212.00 190 200 210 220 Coating weight