Definition of Baidu Encyclopedia: Under certain conditions, the experiment is repeated n times, where nA is the number of times that Event A occurs in n times. If the frequency nA/n gradually stabilizes around a certain value p with the gradual increase of n, 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, and this definition becomes the statistical definition of probability.

Example: Coins are tossed 1000 times, heads are 5 10 times and tails are 490 times, so the frequency of heads is 0.5 1. Coin throwing/kloc-0.000 times, 502 times for heads and 498 times for tails, so the frequency of heads is 0.502. We say the probability of a head is 0.5.