17.8 Bnus, an Icelandic supermarket chain, wants to know the level of consumer satisfaction derived from its

17.8 Bónus, an Icelandic supermarket chain, wants to know the level of consumer satisfaction derived from its four products—A, B, C, and D. The company’s sales records showed that 10,000 customers purchased product A, 18,000 customers purchased product B, 9,000 customers purchased product C, and 14,000 customers purchased product D. Bónus decided to investigate samples of 200 customers, 110 customers, 180 customers, and 150 customers for products A, B, C, and D respectively. From each sample group it was found that that 40% were satisfied with product A, 35% were satisfied with product B, 55% were satisfied with product C, and 15% with product D.

a. Find an estimate of the proportion of customers who were satisfied with the company’s products.

b. Construct a 95% confidence interval for this population proportion.