People often misjudge a person's job by relying on descriptive traits while ignoring base rate probabilities.

Success stories focusing on the "winner" miss how rare it is to get there.

Major life choices should not rely on outlier success stories that ignore basic odds.

In my cognitive psychology class, there’s a section on reasoning and problem-solving where I always ask students to answer a question. It’s a demo originally used by Daniel Kahneman and Amos Tversky.

Steve is very shy and withdrawn, invariably helpful but with very little interest in people or in the world of reality. A meek and tidy soul, he has a need for order and structure, and a passion for detail.

Is he a physician, farmer, salesperson, or librarian?

When I ask students in my class, the overwhelming majority answer "librarian." Why? Because Steve is a meek and tidy soul. He’s introverted. He has his own world. Librarians presumably like to be organized, because you have to organize the books in the stacks. They tend to be quiet and introverted because they like books. So Steve must be a librarian.

The better bet is "salesperson." Why? Because there aren’t a lot of librarian jobs. There are about 140,000 librarians in the United States and more than 13 million people working in sales. Students still say librarian. Why is that?

They pick Steve based on what he is like and ignore how many people hold each job. They’re going by the diagnostic information, the information about the individual, and not the probability that someone holds that........

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