A market research consultant hired by a leading soft drink company wants to determine the proportion of consumers who favor its low-calorie brand over the leading low-calorie competitor in a particular geographic region. A random sample of 250 consumers from the market under investigation is provided in P08_18.xlsx.
a. Find a 90% confidence interval for the proportion of all consumers in this market who prefer the company’s brand.
b. The file contains the gender and age group for each customer in the sample. Find a separate 90% confidence for each gender for the proportion who prefer the company’s brand. Then do the same for each age group. Explain briefly how these confidence intervals compare to each other and to the confidence interval in part a.