12.19 Investment and rate of interest. A market research company wants to study the relationship between y = investment

(in pounds) and x = rate of interest (in percentage), for a British commercial bank. For the last four months, the observations are as shown in the table. The correlation equals 0.857.

Investment Rate of interest 4000 4.0 7000 5.0 8000 6.0 9000 9.0

a. Find the mean and standard deviation for each variable.

b. Using the formulas for the slope and the y-intercept or software, find the regression line.

c. The se of the slope estimate is 364.21. Test the null hypothesis that these variables are independent, using a significance level of 0.05.