To reiterate an important point, you can use a regression model for predicting values of a dependent variable (Y) from an independent variable (X) only within the relevant range of the independent variable. Again, this range is all values from the smallest to the largest X used to develop the regression model. You should not extrapolate beyond the range of X values. For example, when you use the model developed for the moving company data, predictions of labor hours should be made only for moves of 220 through 1,397 cubic feet.
Using the regression model already developed, to predict the mean labor hours for a moving job that consists of 500 cubic feet, you do the following.
|Prediction line for Y||= Y intercept + (slope ...|