Economic growth in China has contributed to increased demand for crude oil and rising gasoline prices ...

Economic growth in China has contributed to increased demand for crude oil and rising gasoline prices in several countries. In May 2013, the mean crude oil imported per day in China was 5.64 million barrels. A random sample of 17 days in the last quarter of 2015 was obtained and the crude oil imported was recorded for each (in million barrels per day, bpd). The summary statistics were = 6.47 million bpd and s = 1.16 million bpd. You may assume that the population is normal. 

a) Should a z or t distribution be used? Remember to explain your answer.

(6 pts.) b) Is there any evidence to suggest that the mean crude oil imported per day in China has changed? Perform the hypothesis test at a 1% significance level. Include the complete four step hypothesis test including all of the work.

(2 pts.) c) Calculate and interpret the 99% confidence interval for the mean.

(1 pt.) d) Explain why parts b) and c) state the same thing. That is, what in part b) is consistent with what in part c).

(1 pt.) e) From the information provided in parts b) – d), do you think the mean crude oil imported per day in China has changed? The precision of the measurement is 0.1 million bpd. Hint: Think about the practicality of the situation.