The way that we find out how well X can predict Y is through the creation of the regression line we mentioned earlier in this chapter. This line is created from data that have already been collected. The equations are then used to predict scores using a new value for X, the predictor variable. Formula 16.1 shows the general formula for the regression line, which may look familiar because you may have used something very similar in a high school or college math course. In geometry, it’s the formula for any straight line: (16.1) where Y ′ is the predicted score of Y based on a known value of X;
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