Suppose there are always n lots, of which m are "medium". The probability of the first person drawn is obviously m/n, and two of the n tags are randomly selected in sequence, and one * * has n(n- 1) methods, which is the total sample space. In these arrangements, to ensure that the second person wins the prize, he has m kinds of lottery methods, so that the first person can choose from the remaining n- 1.
So there are m(n- 1) ways to ensure that the second person wins the lottery. Therefore, the "probability of the second person drawing" is m(n- 1)/n(n- 1), which is still equal to m/n.
Advantages and disadvantages of drawing lots:
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.