How to fold the lottery box

The reason why this question is raised is that lottery tickets have priority and belong to the situation of "going without returning". The man in front drew a lot, but there were fewer lots in the lottery box. Then accordingly. It seems that the probability of the latter person drawing a certain result will change. The reason for this doubt is that the meaning of the word probability is not correctly understood.

What is the probability? Probability is an estimate of unpredictable events. Suppose there are five signatures now. One of the signs is the upper sign. Now two people draw lots. A draws lots first, so what is the probability of B winning the lottery?

There are two situations: A wins the lottery. Obviously, the probability of winning the lottery in A is 1/5. It is impossible for B to win the lottery at this time. It is in this situation. The probability of winning the lottery in B is 0.

When a didn't win the lottery. The probability of Ren Xian A not winning the lottery is 4/5, and the probability of B winning the lottery is 1/4, so the probability of B winning the lottery in the whole process is 4/5× 1/4= 1/5. It can be seen that the winning probabilities of A and B are 1/5.

The key point is that it is impossible to predict the result of A, so the probability that you draw any symbol is the same. But if A knows the result of the lottery after the lottery, then the probability of the second person's lottery will inevitably change. So without knowing the result of the previous person, everyone's probability is the same.