Cronbach’s α (alpha) is a coefficient of reliability. It’s frequently used as a measure of the internal consistency or reliability of a psychometric test score for a sample of examinees. It was initially named alpha by Lee Cronbach in 1951, as he had intended to continue with further coefficients. The measure can be viewed an extension of the classic Kuder-Richardson Formula 20 (KR-20), which is an equivalent measure for dichotomous items. Alpha is not strong against missing data. Several other Greek letters are commonly used by later experts to specify other measures found in a similar context
