kuder

In psychometrics, the Kuder–Richardson Formula 20 (KR-20) first published in 1937 is a measure of internal consistency reliability for measures with dichotomous choices. It is analogous to Cronbach's a, except Cronbach's a is also used for non-dichotomous (continuous) measures. It is often claimed that a high KR-20 coefficient (e.g., > 0.90) indicates a homogeneous test. However, like Cronbach's a, homogeneity (that is, unidimensionality) is actually an assumption, not a conclusion, of reliability coefficients. It is possible, for example, to have a high KR-20 with a multidimensional scale, especially with a large number of items.