Practice question · Numerical answer
Using that table of 100 people, compute the probability that a person is a student given that they like coffee.
Hints
- Restrict attention to the coffee column, then ask what fraction of it is students.
- There are 40 coffee-likers, of whom 30 are students.
Show the answer
0.75 (answers within ±0.005 count)
Why
30/40 = 0.75. Note that P(likes coffee given student) is 30/50 = 0.6 instead, the same joint cell over a different condition. Swapping the two is the most common conditional-probability error, and the table makes the difference visible.
Practise Conditional Probability and Independence
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