A salesman in the consumer-packaged goods industry would like to know if the shelf height in which the product is located in the grocery store affects sales. For one year, the salesman flips a coin every Sunday which determines if his product will be located at eye level or on the bottom shelf that week. Here are the sales (in hundreds of units) for each week: Sales (eye level): 30, 40, 43, 37, 34, 42, 42, 29, 38, 47, 35, 39, 33, 37, 37, 30, 40, 43, 27, 34, 33, 33, 26, 27, 40, 45, 38,28 Sales (bottom shell): 22, 20, 26, 27, 20, 33, 30, 17, 21, 28, 15, 26, 21, 30, 16, 10, 15, 20, 22, 15, 18, 11,20,21 The dotplots of the data are shown. 28 SO 150 35 40 Weekly sales at eye level (hundreds of units) 120 35 10 18 25 30 Weekly sales from the bottom shelf (hundreds of units) (a) Construct and interpret a 99% confidence interval for the true difference in mean weekly sales when the product is located at eye level or on the bottom shelf. (5 points) (b) Does the interval provide convincing evidence that the true mean weekly sales for the two different locations are different? Explain.