Reliability of Katz's Activities of Daily Living Scale when used in telephone interviews.

The reliability of a five-item Katz's Activities of Daily Living (ADL) scale collected by self-report telephone interview is presented. A random sample of 6,472 South Carolina residents over 55 years of age selected from a statewide population is used. Factor structure, Guttman properties, internal consistency reliability, Mokken's index of test homogeneity, and Spearman's coefficient of rank-order correlation are used to show that ADL data gathered by telephone interview are reliable. Because telephone interviewing methods are faster, cheaper, and safer they are recommended as a viable way for researchers, policymakers, and practitioners to gather ADL information.