[EX13-85] It is believed that the amount of nitrogen fertilizer used per acre has a direct effect on the amount of wheat produced. The following data show the amount of nitrogen fertilizer used per test plot and the amount of wheat harvested per test plot.

x, Pounds of Fertilizer y, 100 Pounds of Wheat 30 5 30 9

••• Remainder of data on Student’s Suite CD-ROM.

a. Is there sufficient reason to conclude that the use of more fertilizer results in a higher yield?

Use   0.05.

b. Estimate, with a 98% confidence interval, the mean yield that could be expected if 50 lb of fertilizer was used per plot.

c. Estimate, with a 98% confidence interval, the mean yield that could be expected if 75 lb of fertilizer was used per plot.