A certain brand of apple juice is supposed to have 64 ounces of juice. Because the penalty

Question:

A certain brand of apple juice is supposed to have 64 ounces of juice. Because the penalty for underï¬lling bottles is severe, the target mean amount of juice is 64.05 ounces. However, the ï¬lling machine is not precise, and the exact amount of juice varies from bottle to bottle. The quality-control manager wishes to verify that the mean amount of juice in each bottle is 64.05 ounces so that she can be sure that the machine is not over- or underï¬lling. She randomly samples 22 bottles of juice, measures the content, and obtains the following data:

(a) Because the sample size is small, she must verify that the amount of juice is normally distributed and the sample does not contain any outliers. The normal probability plot and boxplot are shown. Are the conditions for testing the hypothesis satisï¬ed?

(b) Should the assembly line be shut down so that the machine can be recalibrated? Use a 0.01 level of signiï¬cance.
(c) Explain why a level of signiï¬cance of Î± = 0.01 might be more reasonable than Î± = 0.1.