At a time when energy conservation is so important, some scientists think closer scrutiny should be given

Question:

At a time when energy conservation is so important, some scientists think closer scrutiny should be given to the cost (in energy) of producing various forms of food. Suppose you wish to compare the mean amount of oil required to produce 1 acre of corn versus 1 acre of cauliflower. The readings (in barrels of oil per acre), based on 20-acre plots, seven for each crop, are shown in the table.

a. Use these data to find a 90% confidence interval for the difference between the mean amounts of oil required to produce these two crops.
b. Based on the interval in part a, is there evidence of a difference in the average amount of oil required to produce these two crops? Explain.