Estimating the Reliability of Aggregate-Level Variables Based on Individual-Level Characteristics

Social scientists often use the mean of individual-level characteristics to describe aggregates such as organizations, schools, or programs. They seldom, however, attempt to assess the reliability of these measures. This article indicates how the internal consistency reliability of such measures can be estimated for several commonly used research designs. The method is based on generalizability theory and requires only the data that would normally be used to answer the substantive questions of a study; for example retests or parallel forms are not necessary.