Since 1980 the decline in SAT scores has stopped and the scores have started to creep back up. The scores for White Americans have increased 8 points during this period, for nonwhites 15 points. It was, thus, surprising to discover that the overall mean increased only 7 points. This is not an arithmetic error but rather an example of a well-known statistical phenomenon called Simpson's Paradox. In this note we explain the paradox and describe a method which will avoid it in the future. (15pp.)
