Bern Muller’s comments about the proper use of stereotyping are insightful, but need some further discussion to be totally correct. He distinguishes between well-defined group attributes and unknown individual attributes. Statistically men are significantly taller than women, but many women are taller than me. Similarly men on the average have larger lung capacities than women. That enables them to run further on the average. However, the tallest person in the world could well be a woman and the fastest marathoner could be a woman. Even at my prime running condition, I would have placed behind the top hundred or so women in the Boston Marathon. You simply cannot attribute gender to humans based on height, and you cannot predict that a given man will be able to outrun a woman based on average lung capacity differences.
But we cannot infer from these examples that stereotypes cannot be applied to individuals. For instance, if I told you the height of a mature baboon, you could easily infer if it was male or female. The sexual dimorphism demonstrated in baboons is greater than in humans. The separation in sizes is much larger than in humans.
To estimate how valid it is to attribute a group statistic to an individual, we need to know the spread in the value being considered and how much it overlaps the spread from other groups. The distribution of heights in both men and women is broader than the mean difference of the groups. Therefore you are essentially guessing (with a slight probabilistic edge) if you use only height to guess the gender of a human.
But of the group of humans named "Fred", I can pick any at random and guess that specimen is male with a high probability of being correct. If I try the same thing with the group of humans named "Pat", my probability of being correct is much smaller.
So there is both the power of danger of using stereotypes to make decisions about individuals. But even these considerations miss the essential point of why we use stereotypes to make decisions. The ultimate utility of stereotypes is that they are useful. If they were not useful, then they would fall into disuse and we would not have this conversation. We often must make decisions in realtime based on totally inadequate information. In such a situation, we try to fit the data at hand into whatever mental patterns or stereotypes we have stored up from previous experience. If the fit is not perfect, so what? You still have to make a decision. Which way will you jump to avoid a car? American and English pedestrians would probably jump in different directions based on their past history. They each have absorbed stereotypical images of how automobiles move. These images work to save lives when applied in the correct setting, but can endanger lives when used where automobiles drive on the wrong side.
That is one type of hazard. A more common one is the error of attributing to individuals features true for the group when that is not justified. This error is made worse when neither the group nor the parameter is well-defined. Are members of some group less intelligent than some group you are a member of — and therefore you are by definition more intelligent than any member of that group? Start by defining intelligent and then we can spend some time examining the defining groups.
These various pitfalls explain why the term stereotyping has a negative connotation as we mentioned in the last posting. In a sense, the negative connotation derives from the improper derivation of probability from statistics. Much of life is inferring probability from statistics, but they do not tell us that in school.
In response to the interest my original tutorial generated, I have completely rewritten and expanded it. Check out the tutorial availability through Lockergnome. The new version is over 100 pages long with chapters that alternate between discussion of the theoretical aspects and puzzles just for the fun of it. Puzzle lovers will be glad to know that I included an answers section that includes discussions as to why the answer is correct and how it was obtained. Most of the material has appeared in these columns, but some is new. Most of the discussions are expanded compared to what they were in the original column format.