Criterion contamination occurs when the operational or actual criterion includes variance
that is unrelated to the ultimate criterion. Contamination itself may be subdivided into two
distinct parts, error and bias. Error by definition is random variation
(e.g., due to non standardized procedures in testing, individual fluctuations in feelings) and
cannot correlate with anything except by chance alone. Bias, on the other hand, represents
systematic criterion contamination, and it can correlate with predictor measures.