sampling method

There are four common sampling methods:

1. Random sampling, also known as probability sampling, refers to a sampling method in which all basic units in the population have equal chances of being extracted.

2. Systematic sampling, also known as equidistant sampling or mechanical sampling, is to sort the basic units in the survey population according to certain signs, and then sample them in a fixed order and at certain intervals.

3. Stratified sampling, also known as type sampling or classified sampling, is to divide the survey population into several layers, and then randomly select the required number of basic units from each layer to synthesize a survey sample.

4. Cluster sampling, also known as cluster random sampling and cluster sampling, is to divide the whole market survey into several groups in a certain way (such as regions and units), and then take each group as the sampling object and select several groups as the survey samples to conduct a general survey of all basic units in the group.