Correlation

From EvaluationWiki

One in which two properties are tested for, or are found to have, the property of varying together in a regular way; contrasted with a causal study in which one is found to be the cause or effect of the other. This co-variation may be in the same direction (in which case they are said to be 'positively correlated') or in opposite directions (i.e., as one increases, the other decreases, so they are 'negatively correlated'). See also (Stat.)