PSYCHOLOGY
psychology
probability
bias
logic
Base Rate Neglect: Ignoring the Odds
If you hear hooves, think horses, not zebras. Converting specific information into probability requires knowing the base rate.
Tversky & Kahneman• 5 min read
The Shy Librarian
Tom is shy, loves books, and is very tidy. Is Tom more likely to be a Librarian or a Farmer? Most people say Librarian because he fits the stereotype. But there are 20 times more farmers than librarians. So statistically, it is much more likely that Tom is a shy farmer.
The Medical Test
A disease affects 1 in 1000 people. A test is 99% accurate. You test positive. What is the chance you have the disease? Most say 99%. The real answer is less than 10%. Why? Because out of 1000 people, 1 has it (true positive), but 10 healthy people test positive (false positive). So 1 out of 11 is ~9%.