Four people drawing five of seventeen balls overlap
Question
An urn holds balls numbered to . Each of people in turn draws balls () without replacement, records them, and returns all of them to the urn before the next person draws. Let denote the probability that at least one ball is drawn by every one of the people. Compute to three decimal places.
Short answer
About . Apply inclusion–exclusion to the set of balls shared by all draws. A fixed group of balls lies inside one person's draw with probability , hence . Plugging in , , gives , which a simulation confirms.
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Open the worked solutionLessons behind this question
- Counting and Combinatorics
- Sample Spaces, Events, and the Probability Axioms
- Conditional Probability, Total Probability, and Bayes' Rule
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