qOne way to estimate the “badness of fit” is to calculate the scatter:
q
q scatter Sscatter =
q
qThe relation between the scatter to the line of regression in the analysis of two variables is like the relation between the standard deviation to the mean in the analysis of one variable.
qIf lines are drawn parallel to the line of regression at distances equal to ± (Sscatter)0.5 above
and below the line, measured in the y direction,
about 68% of the observation should fall between the two lines.