Toward more robust inferential procedures for coefficient alpha under sampling of both subjects and conditions

Barchard and Hakstian (1997b) demonstrated that inferential procedures used with coefficient alpha are not robust under sampling of both subjects and conditions (Type 12 sampling) with measurement data departing from essentia lly-parallel form. In the first of 2 studies reported here, a sample-based, non-analytical degrees-of-freedom correction factor was empirically develo ped that correlated almost perfectly with the independently-established cor rect degrees of freedom for the data. In the second study, application of t his correction factor was assessed through a comprehensive simulation study involving Type 12 data sets representing a wide range of design characteri stics and manifesting tau-equivalent measurement. Use of the correction fac tor yielded actual Type I error rates closer to nominal values than were ob tained using uncorrected inferential procedures. Implications for practice and future research are discussed.