Discussion of “on State Education Statistics”: A Difficulty with Regression Analyses of Regional Test Score Averages

The Department of Education’s table “State Education Statistics” reports mean test scores by state and mean resource inputs by state. The means are calculated from quite different groups of students, a process we callinconsistent aggregation. We investigate the bias in regression coefficients caused by inconsistent aggregation, first using theoretical calculations, and then by artificially aggregating data from the High School and Beyond sample.