The probability of event A happening is p, so the probability of event A not happening is1-p. If experiment A happens k times, there will be another n-k times not happening. In n experiments, k times that happened once and n-k times that didn't happen happened at the same time, so the probability is multiple.

The probability of event A happening every time must be independent, so the underlined part indicates the number of times that event A happened k times and the number of times that event A didn't happen in n experiments. The whole formula is the probability that event A will happen k times in n experiments.

Independent e

Repeat n times, and this repeated independent test is called N-fold Bernoulli test.

N-fold Bernoulli test is a very important mathematical model, which has a wide range of applications and is one of the most widely used mathematical models. For example, e means flip a coin to get positive or negative, and flip a coin n times. This is the n-fold Bernoulli test.

Suppose that test E can only have two results: "A" and "non-A" call E Bernoulli test.

For example, e means flip a coin to get positive or negative, and flip a coin n times. This is the n-fold Bernoulli test.

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