# S01.10 Bonferroni's Inequality | Summary and Q&A

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April 24, 2018
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S01.10 Bonferroni's Inequality

## TL;DR

The union bound and Bonferroni inequality in probability explain how the probability of an event can be determined based on the probabilities of its subsets.

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### Q: How does the union bound help determine the probability of picking a student who is either smart or beautiful?

The union bound states that the probability of picking a student who is either smart or beautiful is less than or equal to the probability of picking a smart student plus the probability of picking a beautiful student. By summing the probabilities of these individual events, we can determine the upper bound for the probability of picking a student who is either smart or beautiful.

### Q: What is the intuitive content of the Bonferroni inequality?

The Bonferroni inequality states that if most students are smart and most students are beautiful, then the probability of the intersection of the smart and beautiful students' sets is large. This means that there is a high likelihood that a student belongs to both the smart and beautiful sets.

### Q: How can the Bonferroni inequality be generalized to cases with more than two sets?

The Bonferroni inequality can be generalized to cases where we take the intersection of multiple events. If each of these events is almost certain to occur (has a probability close to 1), then the probability of the intersection will be larger than or equal to a value close to 1, which indicates a large probability for the intersection.

### Q: How do DeMorgan's laws come into play in proving these inequalities?

DeMorgan's laws are used to express the complement of an intersection as the union of the complements. By applying DeMorgan's laws, we can rewrite the complement of an event to manipulate the inequalities and derive the desired results.

## Summary & Key Takeaways

• The union bound states that the probability of picking a student who is either smart or beautiful is less than or equal to the probability of picking a smart student plus the probability of picking a beautiful student.

• The Bonferroni inequality states that if most students are smart and most students are beautiful, then the probability of the intersection of the smart and beautiful students' sets is large.

• Both the union bound and Bonferroni inequality can be generalized to cases where we take the intersection of multiple events.