Cronbach's alpha vs. KR20/KR21 in reliability studies

Question

Should we calculate Cronbach's alpha instead of KR20/KR21 for measuring the reliability of an achievement test, or a test with dichotomous data?

Of possible interest: Assessing reliability of a questionnaire: dimensionality, problematic items, and whether to use alpha, lambda6 or some other index?, Omega vs. alpha reliability — chl, Oct 04 '13 at 14:32

score 3 · Answer 1 · answered Oct 04 '13 at 17:08

3

KR 20 is an algebraic simplification of alpha for dichotomous data. If your data are dichotomous then you can use either one -- they will give the same result.

KR 21 is an approximation that is of historical interest only. Don't use it.

answered Oct 04 '13 at 17:08

Ray Koopman

2,303

Cronbach's alpha vs. KR20/KR21 in reliability studies

1 Answers1