4.3 Measuring the Fit of the Regression Model
A regression equation can be developed for any variables X and Y, even random numbers. We certainly would not have any confidence in the ability of one random number to predict the value of another random number. How do we know that the model is actually helpful in predicting Y based on X? Should we have confidence in this model? Does the model provide better predictions (smaller errors) than simply using the average of the Y values?
In the Triple A Construction example, sales figures (Y) varied from a low of 4.5 to a high of 9.5, and the mean was 7. If each sales value is compared with the mean, we see how far they deviate from the mean, and we could ...
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