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Probability set operations

Probability set operations like union, intersection, and complement

This math skill teaches probability set operations such as intersection, union, and complement. Intersection calculates the probability of both events occurring simultaneously, union covers either event happening, and complement involves the probability of an event not happening. Calculations involve multiplication for intersection, addition and subtraction for union, and subtraction from one for complement.

Learn probability set operations

Teaching Transcript

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What do these set operations mean in the world of probability?

The first, with the symbol that looks like the letter 'N', is called intersection. It means the probability of both 'A' and 'B' occurring.

The second, with the symbol that looks like the letter 'U', is called union. It means the probability of either 'A' or 'B' occurring.

The third, with the single apostrophe, is called complement. It means the probability of 'A' not occurring.

To calculate the intersection, we multiply the probabilities because both have to happen.

To calculate the union, we add the probabilities, and then subtract the intersection, because otherwise, the intersection would be counted twice

To calculate the complement, we remember that the probability of 'A' occurring and the probability of 'A' not occurring must add up to 1, or 100 percent, because 'A' either occurs or it doesn't. So the complement is just 1, minus the probability of 'A' occurring.