*** Welcome to piglix ***

Confound


In statistics, a confounder (also confounding variable or confounding factor) is a variable that is correlated (directly or inversely) to both the dependent variable and independent variable.

Confounding is a causal concept, and as such, cannot be described in terms of correlations or associations .

The concept of confounding is defined in terms of the data generating model (as in the Figure above). Specifically, let X be some independent variable, Y some dependent variable. To estimate the effect of X on Y, the statistician must suppress the effects of extraneous variables that influence both X and Y. We say that, X and Y are confounded by some other variable Z whenever Z is a cause of both X and Y.

In the causal framework, denote as the probability of event Y = y under the hypothetical intervention X = x. X and Y are not confounded if and only if the following holds:


...
Wikipedia

...