Why is the probability of the lottery the same?

Set a simple model, such as 10 hand and 10 hand in turn, and everyone has the same probability of 1 hand.

The first person,110.

The second person, (the first person has no winning number1) 9/10 *1/9 =110.

The third person, 9/10 * 8/9 *1/8 =110.

So until the last person is also110.

Extended data:

step

1, number n individuals in the population.

2. Write the number on the number label, put the number label in the container and stir it evenly.

3. Take a batch from it at a time, and take it n times without putting it back.

4. Take out N individuals corresponding to N numbers to obtain a sample with a capacity of N. ..

merits and demerits

The advantage of the lottery method is simple and easy, but the disadvantage is that it is time-consuming, laborious and inconvenient in the case of large overall capacity. If the marked labels are mixed unevenly, it will lead to unfair sampling.

The advantages of random number table method are the same as those of lottery method, but the disadvantage is that it is inconvenient when the overall capacity is large, but it is fairer than lottery method, so these two methods are only suitable for sampling types with small overall capacity.

Baidu encyclopedia-lottery method