The quality-control manager at a compact fluorescent light bulb (CFL) factory needs to determine whether the mean life of a large shipment of CFLs is equal to 7,500 hours. The population standard deviation is 1,080 hours. A random sample of 81 light bulbs indicates a sample mean life of 7,200 hours. a. At the 0.05 level of significance, is there evidence that the mean life is different from 7,500 hours? b. Compute the p-value and interpret its meaning. c. Construct a 95% confidence interval estimate of the population mean life of the light bulbs. d. Compare the results of (a) and (c). What conclusions do you reach? a. Let be the population mean. Determine the null hypothesis, Ho, and the alternative hypothesis, H. Ho:= 7500 H: 7500 What is the test statistic? ZSTAT= (Round to two decimal places as needed.) Suppose that a sample of 200 is selected from a population of 9,000 items. Of these, 10 items are found to have errors of the amounts shown below. 23.35 15.99 33.67 38.74 11.28 26.89 Construct a 95% confidence interval estimate of the total difference in the population. 28.99 31.71 Total differences (Round to two decimal places as needed.) 14.78 33.54