The Daily Decision-15-Conjunction fallacy … when is 2 less than 1?
The Daily Decision-15-Conjunction fallacy
Hello Hello This is Dr. Z, Zachary Brooks, with The Daily Decision
because you want to make better decisions.
Today is the FIFTEENTH episode of The Daily Decision
Linda is 31 years old, single, outspoken, and very bright. When she was in college, she majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in progressive demonstrations.
Which is more probable now?
- Linda is a bank teller.
- Linda is a bank teller and is active in the feminist movement.
Most people say B, but the correct answer is A
This is an example of the conjunction fallacy in decision making and the Linda example is from Kahneman and Tversky 1982.
That is when we hear two things, we automatically add them. After all, 2 is greater than 1 but in probabilities 2 is less than 1.
In Linda’s case, we can assign a 5% probability to Linda being a bank teller and 95% probability of Linda being active in the feminist movement.
When we multiple .05 * .95, we get .0475 which is less than 5%.
When you’re confronted with a decision with multiple parts. Isolate them before considering their connections.
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