There are several methods of sampling survey.

There are the following sampling methods:

1. Simple random sampling: Simple random sampling is the most basic sampling method and the basis of other sampling methods. In simple random sampling, the probability of each case in the population is equal. A certain number of cases are randomly selected from the population, and a sample with good overall representation can be obtained.

2. Stratified sampling: Stratified sampling is to stratify or classify people according to certain characteristics, and then randomly select a certain number of cases from each layer or category to form a sample. Stratified sampling can improve the representativeness of samples, especially when there are great differences between the overall cases. Stratified sampling is usually stratified according to the attribute characteristics of the case, such as age, gender and region.

3. Systematic sampling: Systematic sampling is to arrange all cases in the population in a certain order, then randomly determine the starting position according to the principle of equal distance and extract the next one. Systematic sampling is similar to simple random sampling, but it can save time and resources when the overall scale is large. Systematic sampling is usually suitable for numbering each case in the population.

4. Cluster sampling: Cluster sampling is to divide people into different groups according to certain characteristics, and then randomly select one or several groups to investigate all cases in the selected group. Cluster sampling can improve the representativeness of samples, but it may lead to an increase in sample size and increase the cost of investigation.

5. Subjective sampling: Subjective sampling refers to selecting representative samples in the population according to the subjective experience of the sampler. This method is usually suitable for sampling personnel who have a deeper understanding of the structure and characteristics of the population.

6. Quota sampling: Quota sampling is to classify or stratify people according to certain factors, and then conduct subjective sampling in each layer or category, and allocate a certain sample size for each category. Quota sampling can improve the representativeness of samples, but it may lead to an increase in sample size and increase the cost of investigation.

7. Rolling sampling: Rolling sampling is to determine the next sample according to the information of the previous sample. This method is usually suitable for the situation that the overall scale is large and it is difficult to investigate all cases at once. By taking samples one by one, rolling sampling uses the information of the previous sample to adjust the selection of subsequent samples and improve the representativeness of the samples.