Each car in a sample of seven cars was tested for nitrogen-oxide emissions (in grams per mile), and the following results were obtained: 0.06, 0.11, 0.16, 0.15, 0.14, 0.08, 0.15 (based on data from the Environmental Protection Agency). Assume that nitrogen-oxide emissions are normally distributed for all cars in use in the United States.

a. Assuming that this sample is representative of cars in use in the United States, construct a 95% confidence interval estimate of the mean amount of nitrogen-oxide emissions for all those cars.

b. The Environmental Protection Agency requires that nitrogenoxide emissions be less than 0.165 gram/mile. Someone claims that nitrogen-oxide emissions have a mean equal to 0.165 gram/mile. Does the confidence interval suggest that this claim is valid? Why or why not?