A measure of the relationship between scores. Correlation scores vary between -1.0 and +1.0, with zero indicating no correlation. Scores that are measuring similar things, such as related items on scale or scores on scales measuring the same concept should be highly correlated. Scores that are measuring different things should show a low correlation. It is also possible to have negative correlation scores, indicating an opposing relationship. For example, depression should be negatively correlated with well-being.