Reconsider Prob. 27.9-4. Use the linear regression procedure in the forecasting area of your IOR Tutorial to generate the linear regression line. On the resulting graph that shows this line and the five data points (as blue dots), note that the leftmost data point, the middle data point, and the rightmost data point all lie very close to the line. You can see how the linear regression line shifts as any one of these data points moves up or down by moving your mouse onto the blue dot at this point and dragging it vertically. For each of these three data points, determine whether the linear regression line shifts above this point or shifts below it or still passes essentially through it when the following change is made in one of these data points (but none of the others).
(a) Change the sales from 16 to 19 when the amount of advertising is 225.
(b) Change the sales from 23 to 26 when the amount of advertising is 450.
(c) Change the sales from 20 to 23 when the amount of advertising is 350.