The regression equation y 5 5.0 1 1.0x1 1 2.5x2 has been fitted to 20 data points.

The regression equation yˆ 5 5.0 1 1.0x1 1 2.5x2 has been fitted to 20 data points. The means of x1 and x2 are 25 and 40, respectively. The sum of the squared differences between observed and predicted values of y has been calculated as SSE 5 173.5, and the sum of squared differences between y values and the mean of y is SST 5 520.8. Determine the following:

a. The mean of the y values in the data.

b. The multiple standard error of estimate.

c. The approximate 95% confidence interval for the mean of y whenever x1 5 20 and x2 5 30.

d. The approximate 95% prediction interval for an individual y value whenever x1 5 20 and x2 5 30.

( DATA SET ) Note: Exercises 16.18–16.22 require a computer and statistical software. If possible with your statistical software, determine the exact, rather than the approximate, intervals.