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.

a. What does the boxplot suggest about the status of the specification for true average coating weight?
b. A normal probability plot of the data was quite straight. Use the descriptive output to test the appropriate hypotheses.

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