8 Suppose you fit the first-order multiple-regression model y = b0 + b1 x1 + b2 x2 + e to n = 25 data points and obtain the prediction equation yn = 6.4 + 3.1x1 + .92x2 The estimated standard deviations of the sampling distributions of b n

1 and b n

2 are 2.3 and .27, respectively.

a. Test H0: b1 = 0 against Ha: b1 7 0. Use a = .05.

b. Test H0: b2 = 0 against Ha: b2  0. Use a = .05.

c. Find a 90% confidence interval for b1. Interpret the interval.

d. Find a 99% confidence interval for b2. Interpret the interval.