a quantitative independent variable

a variable that may affect the relationship between two variables of interest, but is not of intrinsic interest itself

A product of the correlation of two related variables times their standard deviations. Used in true experiments to measure the difference of treatment between them.

A variable that is used in an analysis to correct, adjust, or modify the scores on a dependent variable before those scores are related to one or more independent variables. For example, in an analysis of how demographic factors (age, sex, education, etc.) relate to wage rates, monthly earnings might first be adjusted to take account of (i.e., remove effects attributable to) number of hours worked, which in this example would be the covariate.

A secondary variable that influences the outcome of an experiment.

The potentially confounding variable controlled for in analysis of covariance.

(Also called covariable.) An independent variable, or predictor, in a regression equation. Also, a secondary variable that can affect the relationship between the dependent variable and independent variables of primary interest in a regression equation.

In statistics, a covariate is a variable that is possibly predictive of the outcome under study. A covariate may be of direct interest or be a confounding variable or effect modifier.