Generalizability theory distinguishes between state and trait anxiety.

Accurate distinction between state and trait anxiety is necessary for assessment and monitoring of individual anxiety levels over time and developing effective interventions to reduce anxiety. Generalizability theory (G-theory) is a suitable method to distinguish between state and trait and to evaluate reliability of test scores and sources of measurement error in the assessment of affective conditions. We applied G-theory to the widely used 40-item State and Trait Anxiety Inventory (STAI) completed by 139 participants on three occasions separated by 2-week intervals. The results show that both subscales of the STAI demonstrated excellent reliability for test scores in measuring trait anxiety with high generalizability of scores across occasions and persons (