What is the difference between a pure strategy and a mixed strategy?

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In game theory, the distinction between pure and mixed strategies lies in how a player selects their course of action:

  • Pure Strategy: A player chooses a single, specific action or move consistently. When a game has a saddlepoint, a pure strategy exists that represents the best possible choice for each player.1
  • Mixed Strategy: A player chooses from a set of available actions according to a specific probability distribution. This approach is used when no single best strategy exists, as it prevents an opponent from exploiting predictable patterns in behavior.1

In many games, such as rock-paper-scissors, a mixed strategy is necessary to reach a Nash equilibrium, as choosing any single option consistently would allow an opponent to gain an advantage. The minimax theorem establishes that every finite, two-person constant-sum game has a solution involving either pure or mixed strategies, ensuring that players can enforce an optimal expected payoff.21