ABSTRACT
So far we have examined individual variables dealt with one at a time. Much psychological research depends not on the analysis of variables taken in isolation but on the interrelationships between variables. More often than not, psychologists investigate the relationship between at least two variables. For example, is there a relationship between extraversion and criminality? Is there a relationship between age and speed of reaction time to a stimulus? Is there a relationship between intelligence and income? In each of these cases, there are two separate variables we wish to relate to each other. Statistics provides both numerical and graphical methods of describing the size of these relationships.
