PURPOSE This study explores how highly correlated time variables (occupational cohort time scales) contribute to confounding and ambiguity of interpretation. METHODS Occupational cohort time scales were identified and organized through simple equations of three time scales (relational triads) and the connections between these triads (time scale web). The behavior of the time scales was examin...

There is also a growing consensus that evidence of teachers’ contributions to student learning should be a component of teacher evaluation systems, along with evidence about the quality of teachers’ practice. “Value Added Models” (VAMs) for looking at gains in student test scores from one year to the next are promoted as tools to accomplish this goal. Policy makers can benefit from research abo...

In 1999, Medicare implemented a resource-based relative value unit (RVU) system for physician practice expense payments, and increased the number of services for which practice expense payments differ by site. Using 1998-2004 data, we examined RVU growth and decomposed that growth into resource-based RVUs, site of service, and service quantity and mix. We found that the number services with sit...