My random reading in matters mathematical has brought me to Simpson's Paradox, the idea that a clear trend in a group of data can disappear, or even reverse, when different groups of data that taken severally exhibit the same trend are aggregated. It is named for Edward Simpson, who described the effect in "The Interpretation of Interaction in Contingency Tables" in the Journal of the Royal Statistical Society in 1951. Colin Blyth rediscovered this paper and gave the phenomenon the name Simpson's Paradox in a 1972 paper. It was once referenced in an episode of the prime-time cartoon The Simpsons because ... well, the name. Wikipedia has a good discussion. This is not really a "paradox" at all, though the name will probably stick. It wouldn't impress Zeno, or whoever started the thing about the lying Cretan. But the phrase "Simpson's odd-seeming phenomenon" doesn't seem very resonant. Good brief discussion in pp. 70 - 72 of Titel...