The Effect of Measurement Errors on Apparent Group Level Effects in Educational Progress

Aggregated group-level effects (AGLEs) are widely considered to be an extremelyimportant aspect of learning. However some authors have implied that many apparentfindings of such effects are spurious and arise because of omission or inadequatemeasurement of pre-existing differences. This study considers a further trap, inwhich the appropriate variables are included, but are measured with error.It shows allowing for measurement error does in fact impact on apparent AGLEs,and that the effects of allowing for measurement error, while apparently inconsistent,can largely be explained as increasing the apparent effect of a variable, and decreasingthe apparent effects of other correlated variables.