1. The simple random sampling method is to randomly select all samples, and the probability of each sample being selected is the same.
For example:1-100, a number is randomly selected, and the probability of each tree being selected is the same, which is one percent.
2. Systematic sampling is to take samples according to the rules prepared in advance.
For example:1-100, according to the rules prepared in advance, one is drawn every 10, and the numbers drawn are:10, 20, 30, 40, 50, 60, 70, 80, 90,/.
3. Stratified sampling is to divide and extract all samples according to a certain proportion.
For example:1-100, every ten numbers are divided into ten groups, and the probability of each number in each group is the same, which is one tenth.
Extended data:
The characteristics of simple random sampling are: the probability of each sample unit being extracted is equal, and each unit of the sample is completely independent, and there is no certain correlation and exclusion between them.
1. Simple random sampling requires that the total number of samples sampled n is limited.
2. Extract simple random samples from the population one by one.
3. Simple random sampling is a kind of sampling that cannot be put back.
4. The sampling probability of each individual sampled systematically is n/n. ..
References:
Baidu encyclopedia-sampling method