Variable

A characteristic that takes on different values or expressions.

Variables are used to measure concepts. For example, intelligence is a concept that may be measured by the variable of IQ scores: scores obtained on a particular test of intelligence. IQ scores range from values of 0 to 200, with higher scores indicating greater amounts of intelligence (according to the way in which the concept is defined).

The concept of lung cancer may be measured by the variable of the presence or absence of a tumor on the lungs — a variable that has only two values (you either have a tumor or you don’t).

The concept of memory may be measured in many ways. For example, we might give people a list of twenty words to memorize and then, at some later time, ask them to recall as many of the words as possible. In this case, the concept of memory is measured by the variable of the number of items recalled from a word list.