[Member (365WT)]answers [Chinese ]  Time :20191023  Also known as random sampling. Probability sampling is based on the probability theory and the random principle to extract the sample, so that each unit in the population has a previously known nonzero probability to be sampled. The overall unit is drawn. The probability can be specified by the sample design, through some randomization operation. Although the random sample is generally not exactly the same as the whole, it is based on the law of large numbers, and can calculate and control the sampling error, so it can Properly explain to what extent the statistical value of the sample is suitable for the population. According to the results of the sample survey, the population can be inferred quantitatively, and the nature of the population can be explained to some extent..Probability sampling is mainly divided into simple random sampling, systematic sampling, classified sampling, cluster sampling, multistage sampling, etc. Most reallife sampling surveys use probability sampling methods to extract samples... 
