Fuel Tank Capacity. Consumer Reports provides informa- tion on new automobile models-including price, mileage rat- ings, engine size, body size, and indicators of features. A simple random sample of 35 new models yielded the following data on fuel tank capacity, in gallons.
17.2 23.1 17.5 15.7 19.8 16.9 15.3 18.5 18.5 25.5 18.0 17.5 14.5 20.0 17.0 20.0 24.0 26.0 18.1 21.0 19.3 20.0 20.0 12.5 13.2 15.9 14.5 22.2 21.1 14.4 25.0 26.4 16.9 16.4 23.0
a. Find a point estimate for the mean fuel tank capacity of all new automobile models. Interpret your answer in words. (Note: x i = 664.9 gallons.)
b. Determine a 95.44% confidence interval for the mean fuel tank capacity of all new automobile models. Assume σ = 3.50 gallons.
c. How would you decide whether fuel tank capacities for new automobile models are approximately normally distributed?
d. Must fuel tank capacities for new automobile models be ex- actly normally distributed for the confidence interval that you obtained in part (b) to be approximately correct? Explain your answer. 8.8 Home Improvements. The American Express Retail Index.