Définition Bias

A bias or a distortion results from an error of data collection, leading to erroneous results of an investigation. One speaks of the systematic and random bias.

Systematic errors can arise for example in the sample selection (selection bias). Trying to figure out the most popular basketball team in the U.S. by asking only people in L.A. would thus provide a highly distorted result. Another form of systematic distortion may be ‘socially desired’ false statements (social desirability bias).

See also the effect of social desirability. Random distortions are referred to as bias, which cannot be traced to a causal relationship.