ABSTRACT
With each value of the variable y there may be associated the value of another variable x. Both variables may be of equal stature and interest, and the statistical problem is to investigate the relationship between them. In other instances, the variable x may be a baseline value against which the value of the primary variable y should be compared, or x may be an explanatory variable whose effect on the primary variable y should be adjusted for or standardized. The ap propriate analyses for these situations are the topics of this chapter and the next.
