What is the first probability sampling? What is the basic method? Examples are given to illustrate the characteristics and applicability of simple random sampling.

Simple random sampling, stratified sampling and systematic sampling. Simple random sampling: lottery method, random number table method. Stratified sampling: find the proportion and sample size. Systematic sampling: grouping and segmentation. The characteristics of simple random sampling: the number of samples is limited and the possibility is equal. Applicability: Overall, the sample size is small.