A latent state-trait model for analyzing states, traits, situations, method effects, and their interactions.

OBJECTIVE: Studies on situation and Person × Situation interaction effects often use only one method of measurement, so that the extent to which the effects may be method-specific cannot be determined. We introduce a new multimethod latent state-trait model for random and fixed situations (MM-LST-RF), which allows examining person, situation, and Person × Situation interaction effects in the context of multimethod measurement designs (e.g., studies with multiple reporters), and discuss potential areas of application for the new model in personality research.

METHOD: The new model allows analyzing novel features of multimethod, multi-situation data, including (a) the convergent validity and method specificity of trait (person) effects, situation effects, and Person × Situation interaction effects; (b) the degree of situation specificity of method effects; and (c) potential Method × Situation interactions. An application to smoker's affect (N = 235; 57% female; 93% Caucasian) before and after quitting smoking is presented with positively and negatively worded items as methods.

RESULTS: The MM-LST-RF model fit the smoking data well. Method specificity of many effects was high.

CONCLUSIONS: The MM-LST-RF model provides researchers with a new framework for testing method specificity of person, situation, and interaction effects.