- 1. A situation in which the effects of two or more processes are not separated; the distortion of the apparent effect of an exposure on risk, brought about by the association with other factors that can influence the outcome. 2. A relationship between the effects of two or more causal factors observed in a set of data, such that it is not logically possible to separate the contribution of any single causal factor to the observed effects.
* * *con·found·ing (kon-founґding) interference by a third variable so as to distort the association being studied between two other variables, because of a strong relationship with both of the other variables; a relationship between two causal factors such that their individual contributions cannot be separated.
Medical dictionary. 2011.