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What does probability mean?
Probability, also known as "probability", reflects the probability of random events. Random events refer to events that may or may not occur under the same conditions.

For example, it is a random event to randomly select one from a batch of goods with genuine products and defective products, and "what is extracted is genuine products". Suppose a random phenomenon is tested and observed n times, in which event A appears m times, that is, its frequency is m/n. After a lot of repeated experiments, m/n is often closer to a constant (see Bernoulli's law of large numbers for details). This constant is the probability of the occurrence of event A, which is usually expressed by P (A).

Statistical definition

Under certain conditions, the experiment was repeated n times, where nA is the number of times that Event A occurred in n times. If with the gradual increase of n, the frequency nA/n gradually stabilizes around a certain value p, then the value p is called the probability of the occurrence of event A under this condition, and it is recorded as P (a) = P .. This definition is called the statistical definition of probability.

In history, Jacob Bernoulli is the first person to give a strict meaning and mathematical proof to the assertion that "when the number of experiments n increases gradually, the frequency nA is stable at its probability p".

From the statistical definition of probability, it can be seen that the numerical value p is a quantitative index to describe the possibility of event A under this condition.