In a simple regression the regression equation is Y^ = 5X 7. Now if we interchange the X and Y data (that is, what was originally X is now Y and vice versa) and repeat the regression, we would expect the slope of the new regression line to be exactly equal to 1/5 = 0.2.
But the slope will only be approximately equal to 0.2 and almost never exactly equal to 0.2. Why?