coefficient alpha

n. An index of the internal consistency of a set of items which can have more than two possible responses which is the average of all possible split-half correlation coefficients corrected for attenuation. Coefficient alpha is a derivative of Kuder-Richardson formula 20 (KR20), which performs the same function for tests in which only one of two answers is possible for each item. Coefficient alpha is strongly related to the length of the scale so that scales with a length greater than 100 items always approach 1.00, or perfect consistency. Also called Cronbach's alpha.