11.78 Based on a sample of 18 observations, the population regression model yi = b0 + b1xi + ei was estimated. The least squares estimates obtained were as follows:

b0 = 5 and b1 = 2.2 The total and error sums of squares were as follows:

SST = 78 and SSE = 49

a. Find and interpret the coefficient of determination.

b. Test, against a two-sided alternative at the 5% significance level, the null hypothesis that the slope of the population regression line is 0.

c. Find a 95% confidence interval for b1.