The Maudsley Obsessive-Compulsive Inventory: A reliability generalization meta-analysis1

The Maudsley Obsessive-Compulsive Inventory (MOCI) is one of the most used tests in clinical psychology for assessing the obsessive and compulsive symptoms in psychiatric patients and as a screening tool in nonclinical population. A reliability generalization meta-analysis was carried out with the purpose of studying how test scores reliability varies along different applications of this test. An exhaustive search of the literature enabled us to select 51 studies that reported some reliability estimate and, by means of the KR-21 formula, we were able to increase the database to 308 internal consistency reliability estimates. On average, the internal consistency reliability of test scores was .76 for the original 30-items version. The reliability coefficients exhibited a large heterogeneity. The analyses of moderator variables revealed a predictive model composed of two predictors: the standard deviation and the mean of test scores. Our results confirmed that reliability is not a property of the test itself, but it varies from one application to the next. As a consequence, the erroneous practice of inducing reliability from previous studies should be avoided in psychological research.