While the significance of principals' roles is widely recognized, and the impactful behaviors of principals are empirically delineated, little is known about whether principals spend time in an impactful way, whether principals' time use varies across different school contexts, or whether principals' time use is related to critical school…

This tutorial addresses possible sources of confusion in interpreting trait scores from the bifactor model. The bifactor model may be used when subscores are desired, either for formative feedback on an achievement test or for theoretically different constructs on a psychological test. The bifactor model is often chosen because it requires fewer…

In PISA 2009, Finland and Singapore were both ranked high among the participating nations and have caught much attention internationally. However, a secondary analysis of the means for Reading achievement show that the differences are rather small and are attributable to spurious precision. Hence, the two nations should be considered as being on…