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Reaching a two-point lead with a 30 percent edge

Question

Alice and Bob play a series of basketball games starting from a score of 00 each. Alice wins any game with probability 0.30.3, independently. The winner of a game gains a point and the loser drops a point, and the set goes to the first player to reach 22 points. What is the probability Alice wins the set?

Short answer

958\tfrac{9}{58}. Points move in lockstep, so the set ends when one player wins two games in a row from a tied position; a split pair resets it. Alice wins a pair with probability 0.090.09 and Bob with 0.490.49, so Alice wins with probability 0.090.58\tfrac{0.09}{0.58}.

Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.

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