Complete Information - Certain Information

Certain Information

A distinction is made by some authors of game theory literature between complete and certain information. In this context, complete information is used to describe a game in which all players know the type of all the other players, i.e. they know the payoffs and strategy spaces of the other players. Certain information is used to describe a game in which all players know exactly what game they are playing in the sense that they know what the payoff of playing a particular strategy will be given the strategies played by other players. An equivalent way of making the distinction, particularly helpful in the context of extensive form games, is to define a game of incomplete information as any game in which nature moves first and to define a game of uncertain information as any game in which nature moves after the players have moved.