It has been proposed that there is a difference in the number of hours of TV watched per week by “good students” (B average or better) versus “poor” students (D average or worse). You take a simple random sample of 1400 “good” students and find that the average weekly TV hours for the sample is 22.4, with sample standard deviation of 4.7 hours. For a sample of 1000 “poor” students, the weekly average is 31.5, with a standard deviation of 6.1 hours.
a. Build and interpret the 99% confidence interval estimate of the population average difference in TV watching hours for “good” students vs. “poor” students.
b. Suppose sample sizes were in fact 14 “good” and 10 “poor” students. Revise your interval and discuss the changes.
c. For part b, what population assumptions did you make? 80. Othello Moore of Venice, a fashion retailer, wants to establish the difference in average in store purchases for customers under the age of 25 and customers 25 or older. He selects a simple random sample of 50 customers under 25 and 50 customers 25 and older. For the under 25 sample, purchase amounts average $ 163.50, with standard deviation of $ 45.