The concurrent validity of alcohol trait severity was tested in three steps. First, correlations between the IRT-derived continuum score and other indicators of alcohol severity from Project MATCH were computed, providing an initial estimate of concurrent validity with alternative markers of the severity construct. Second, correlations with other variables that have established relations with alcohol severity were computed, and compared with analogous correlations with other alcohol severity variables used in the study. Finally, the incremental validity of alcohol trait severity was tested by computing partial correlations between it and the external variables, controlling for the effects of other severity markers. This final set of analyses tested the ability of the empirically-derived continuum to provide more information than commonly used alternatives.
