Temporal stability of the intrinsic motivation inventory.
To examine the temporal stability of the Intrinsic Motivation Inventory a Greek version was administered to 144 undergraduate students after an endurance field test. The same procedure was repeated one week later. Factor analysis followed by varimax rotation showed that three factors (Perceived Competence, Interest/enjoyment, and Effort/importance) explained 65.26% of the total variance. Computed intraclass correlation coefficients (ICC) were .61 for the Perceived Competence subscale, .86 for the Interest/enjoyment, .60 for the Effort/importance, and .70 for the overall scale. The results, however, were modified when the sample was divided in two groups. The first represented small changes in perceived competence between the first and the second measurement, while the second one represented large changes between the two measurements. Recalculated intraclass correlation coefficients for individuals whose Perceived Competence score remained relatively stable yield a high value (.92), whereas individuals whose Perceived Competence changed yield an extremely low value (.60). It was concluded that the Intrinsic Motivation Inventory provides a temporally stable measure, given that perceived competence has not been markedly changed.