2-1.1 Explanatory variables.
Whenever we consider two records relating to the same kind
of entity, the pair is either matched or unmatched. They are matched when they represent the same
entity in the real world and unmatched when they don't. To study this characteristic of a pair
statistically, we set up a variable that is true if the pair is matched and false if the pair is unmatched.
This is the salient characteristic of what statisticians call the explanatory variable. It is the value of
this variable that the statistics are supposed to explain. The statistics will help us, for example, to
determine the probability that the pair is matched (or unmatched). The investigator must only
assume that this value is an inherent property of the pair, that the fact that the pair is matched (or not)
explains why her measurements come out the way they do.
