Reliability is the degree to which an assessment tool produces stable and consistent results. Internal consistency is a measure of reliability used to evaluate the degree to which different test items meant to assess the same construct yield similar results. This app calculates the various reliability/internal consistency measures of assessment tools such as Test Retest reliability, Spearman–Brown reliability, Cronbach's alpha, Kuder-Richardson 20, Kuder-Richardson 21, Guttman Lambda 1, Guttman Lambda 2, Guttman Lambda 3, Guttman Lambda 4, Guttman Lambda 5, Rulon and Flanagan