The strange assumption that a group’s distribution of measurements could safely be substituted for an individual’s distribution of measurements was implicitly accepted by almost every scientist who studied individuals, though most of the time they were hardly conscious of it. But after a lifetime of mathematical psychology, when Molenaar unexpectedly saw this unjustifiable assumption spelled out in black and white, he knew exactly what he was looking at: an irrefutable error at the very heart of averagarianism.
