APA Dictionary of Psychology

a systematic error in some particular direction. Constant error is computed as the average positive or negative difference between the observed and actual values along a dimension of interest. For example, if a weight of 1 kg is judged on average to be 1.5 kg, and a weight of 2 kg is judged to be 2.5 kg, the constant error is 500 g. See also absolute error; random error.