Refer to the American Secondary Education (Fall 2009) study of middle school students’ usage of laptop computers, Exercise 2.100 (p. 72). Recall that for a sample of 106 students, the researchers reported the following statistics on how many minutes per day each student used a laptop for taking notes: = 13.2,5 = 19.5. Now the researchers want to estimate the average amount of time per day laptops are used for taking notes for all middle school students across the country.

a. Define the target parameter for the researchers in words and symbols.

b. In Exercise 2.100a, you computed the interval, ± 2s. Explain why this formula should not be used as an interval estimate for the target parameter.

c. Calculate a 90% confidence interval for the target parameter. Interpret the result.

d. Explain what the phrase “90% confidence” implies in your answer to part c.

e. In Exercise 2.100b you concluded that the distribution of laptop usage for taking notes for the sample of 106 students cannot be symmetric. Consequently, the distribution cannot be normal. Does this compromise the validity of the interval estimate, part c? Explain.