The scatterplot to below shows the relationship between the Identical Blocks Test (a measure of spatial ability) and the Wonderlic Test (a measure of general intelligence). As you can see, the relationship is fairly strong: Pearson's correlation is 0.677.

The best fitting straight line is also shown. It has a slope of 0.481 and a Y intercept of 15.8468. (Click here to see how to compute the slope and intercept and the criterion for deciding best fit.) The regression line can be used for predicting. From the graph, one can estimate that the score on the Wonderlic for someone scoring 10 on Identical Blocks is about 20.

From the formula for Y', it can be calculated that the predicted predicted score is 0.481 x 10 + 15.86 = 20.67.