Simpson's Paradox in a nutshell

Norm Matloff points us to a pithy example that sums up Simpson's Paradox perfectly, captured in the title of a medical paper: "Good for Women, Good for Men, Bad for People". He explains how Simpson's Paradox isn't a paradox at all, but just the consequence of including a minor variable in a model ahead of a more significant variable, and illustrates this with an R analysis of the UCB admissions data. You can also see an interactive analysis of the same data here.