The Western Collaborative Group Study was carried out in California in 1960-1961. 
One goal was to explore any associations between behavior patterns and 
risk of coronary heart disease.  These data are a subset of the original 3,154
middle-aged men: those 38 men who weighed at least 225 pounds. Group 1 participants
are those judged to be of Type A behavior, characterized by urgency, ambition,
and aggression. Group 2 participants are those judged to be of Type B behavior,
which is relaxed, non-competitive, and less hurried. The outcome here is total
cholesterol, which when elevated above "normal" values is a risk factor for coronary 
heart disease.

These data appeared in: Everitt B and Rabe-Hesketh S (2001). Analyzing
Medical Data Using S-Plus. New York: Springer-Verlag Inc.