1. The following data show the costs charged by a tax preparation service for a random sample of 15 tax returns. $ 135 $ 120 $ 150 $ 110 $ 90 $ 115 $ 130 $ 200 $ 180 $ 200 $ 140 $ 150 $ 100 $ 75 $ 70 a. Using a 98% confidence interval, estimate the average cost of the service for preparing a tax return for a customer. b. What is the margin of error for this sample? c. Verify your result using Excel. d. What assumptions are necessary for this analysis?2. The makers of compact uorescent light bulbs (CFL) claim the bulbs use ?5% less energy and last 10 times longer than incandescent bulbs. A 16-watt CFL (equivalent to a 60-watt incandescent) has a rated lifetime ot 8,000 hours. To test this claim, a random sample of 50 CFLs was drawn. and the average life of a bulb was determined to be 7,960 hours. Assume the standard deviation for the life of CFL bulbs is 240 hours. a. Does this sample provide enough evidence to support the claim that CFLs average 8,000 hours .with 95% condence? b. what is the margin of error for this sample using a 95% confidence interval? c. Verify your result using Excel. 3. Certain advertisers would like to estimate the proportion of viewers who spend the majority 01 their television time watching alone. The consensus is that this percentage has been increasing over the years due to the increased number of television sets in U.S. households. a. Determine the sample size needed to construct a 90% confidence interval with a margin of error no more than 5% to estimate the true proportion 01 viewers who watch television alone. I]. what impact would a pilot sample that showed that 38% of viewers spend the majority of their television time watching alone have on your results