Front housings for cell phones are manufactured in an injection molding process. The time the part is allowed to cool in the mol

d before removal is thought to influence the occurrence of a particularly troublesome cosmetic defect, flow lines, in the finished housing. After manufacturing, the housings are inspected visually assigned a score between 1 and 10 based on their appearance, with 10 corresponding to a perfect part and 1 corresponding to a completely defective part. An experiment was conducted using two cool-down times, 12 and 24 seconds, and 20 housings were evaluated at each level of cool-down time. All 40 observations in this experiment were run in random order. The data are as follows:10 Seconds 20 Seconds1 3 7 62 6 8 91 5 5 53 3 9 75 2 5 41 1 8 65 6 6 82 8 4 53 2 6 85 3 7 7 a. Is there evidence to support the claim that the longer cool-down time results in fewer appearance defects? Use α= 0.05. b. What is the P-value for the test conducted in part (a)? c. Find a 95 percent confidence interval on the difference in means. Provide a practical interpretation of this interval. d. Draw dot diagrams to assist in interpreting the results from this experiment. e. Check the assumption of normality for the data from this experiment.