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  • STA256 Lecture 03

Addition Law of Probability

• $P(A\cup B)=P(A)+P(B)-P(A\cap B)$
• This also doesn't care if they're disjoint or not, this works on any sample space.
• $P(A\cup B)=P(A)+P(B)-P(A\cap B)$
• We subtract the middle part because it was counted twice.