Classical probability is also called traditional probability, and its definition was put forward by French mathematician Laplace. If a random test contains limited unit events and the possibility of each unit event is equal, then this random test is called Laplace test, and the probability model under this condition is called classical probability model. Under this model, all possible results of random experiments are limited, and the probability of each basic result is the same. For example: ① In the experiment of tossing a coin (a coin with uniform texture), only heads or tails may appear. Because of the symmetry of coins, it is always considered that the possibility of heads or tails is the same; (2) If a dice with uniform texture is thrown, each of the six possible points is equally possible; (3) Another example is the sampling inspection of limited products with the same appearance, which also belongs to this mode. Classical probability is the most intuitive and simple model in probability theory, and many operational rules of probability are obtained for the first time under this model.