claim: Your odds of correctly guessing the outcome of a flipped coin are 1 in 2, but your odds of guessing correctly twice in a row are only 1 in 4 —
evidence: P ( A  or  B ) = P ( A ∪ B ) = P ( A ) + P ( B ) − P ( A ∩ B ) = P ( A ) + P ( B ) − 0 = P ( A ) + P ( B ) {\displaystyle P(A{\mbox{ or }}B)=P(A\cup B)=P(A)+P(B)-P(A\cap B)=P(A)+P(B)-0=P(A)+P(B)} For example, the chance of rolling a 1 or 2 on a six-sided die is P ( 1  or  2 ) = P ( 1 ) + P ( 2 ) = 1 6 + 1 6 = 1 3 .