We have all been told in school not to stereotype. In one class, a teacher provided us a list of people and asked “which ones would you most like to live by?” She then listed all the normal sounding ones and said they were secret axe murders (and the like). And then she took all the oddball ones and said they we upstanding citizens. I tried to point out anyone could make up any story, but she would not buy it. The real truth is that “Stereotypes are more valid than most social psychological hypotheses”. From psychologytoday:

Except stereotypes are not inaccurate. There are many different ways to test for the accuracy of stereotypes, because there are many different types or aspects of accuracy. However, one type is quite simple — the correspondence of stereotype beliefs with criteria. If I believe 60% of adult women are over 5′ 4″ tall, and 56% voted for the Democrat in the last Presidential election, and that 35% of all adult women have college degrees, how well do my beliefs correspond to the actual probabilities? One can do this sort of thing for many different types of groups.

And lots of scientists have. And you know what they found? That stereotype accuracy — the correspondence of stereotype beliefs with criteria — is one of the largest relationships in all of social psychology. The correlations of stereotypes with criteria range from .4 to over .9, and average almost .8 for cultural stereotypes (the correlation of beliefs that are widely shared with criteria) and.5 for personal stereotypes (the correlation of one individual’s stereotypes with criteria, averaged over lots of individuals). The average effect in social psychology is about .20. Stereotypes are more valid than most social psychological hypotheses.