Quiz 6 Solution

Randomly select a woman from the U.S.  Which event is more likely and why:
a) She is a truck driver
b) She is a truck driver who identifies as a feminist

Almost everyone got this one correct.  (a) is more likely, simply because there are most probably more female truck drivers than female truck drivers who are feminists.  At the very most, these two probabilities might be equal (if all female truck drivers were feminists),but if even one female truck driver is not, then (a) will have a higher probability than (b).

This is a semi-famous question.  A well-known psychological study done in the 60's asked a random sampel of adults a similar question (about a bank teller named Linda who was or was not a feminist) and found that people overwhelmingly chose (b):  Linda was more likely to be a bank teller active in the feminist movement.  Why?  Because the brain does a bad job with probabilities.  Which is why some formal training -- and careful thinking -- is required before answering probability questions.