Non-spherical errors, namely heteroscedasticity, serial correlation and cross-sectional correlation are commonly present within panel data sets. These can cause significant problems for econometric analyses. The FGLS(Parks) estimator has been demonstrated to produce considerable efficiency gains...

Our study empirically investigates the relationship between constructed-response (CR) and multiple-choice (MC) questions using a unique data set compiled from several years of university introductory economics classes. We conclude that CR and MC questions do not measure the same thing. Our main...