By Arnold Kling
John Pinkerton writes (on Facebook),
I always interpreted the bank teller probability as “If I were to tell you that Linda is a bank teller and is active in the feminist movement, how likely would you think I was correct?” For this meaning, if you describe someone in greater detail, it’s more likely you know them well and thus describe them accurately.
This is a plausible explanation. However, I have seen students wrestle with such problems when they are presented as a question of whether the sequence of coin flips HHT has higher probability than the sequence HHTT. Pinkerton’s comment is on Steven Poole’s article. About the bank teller example, Poole writes
Tellingly, the psychologists Ralph Hertwig and Gerd Gigerenzer reported in 1999 that when you give people the same puzzle and ask them to guess about relative frequencies instead of what is more ‘probable’, they give the mathematically correct answer much more often. One might add that, if we are talking plausibility, the notion that Linda is a bank teller and an active feminist fits the whole story better. Arguably, therefore, it is a perfectly rational inference: all the available information is now consistent.
The entire article is recommended.
Source: About a Common Probability Error