Sampling survey is a kind of incomplete survey, which is a survey method to select some units from all the survey objects and estimate and infer all the survey objects accordingly. Obviously, although sampling survey is not a comprehensive survey, its purpose is to obtain information reflecting the overall situation, so it can also play the role of a comprehensive survey.

According to the sampling method, sampling survey can be divided into probability sampling and non-probability sampling. Probabilistic sampling is based on the principles of probability theory and mathematical statistics, selecting samples from the investigated population, quantitatively estimating and inferring some characteristics of the population, so that possible errors can be controlled in a probabilistic sense. Probabilistic sampling is customarily called sampling survey.

Scope of application of sampling survey

First, things that cannot be fully investigated. Some things are destructive when measured or tested, and it is impossible to conduct a comprehensive investigation. For example, the seismic test of TV, the durability test of light bulbs and so on.

Second, some things can be comprehensively investigated in theory, but in fact they cannot be comprehensively investigated. For example, know how many trees there are in a forest and how the family life of employees is.

Thirdly, sampling survey method can be used for quality control in industrial production.

Fourthly, by means of sampling inference, we can test a general hypothesis, judge whether it is established or not, and decide whether to accept it or not.