Simple random sampling. Simple random sampling, also known as pure random sampling, is a method of sampling from the total amount and conducting random investigation without any grouping arrangement in advance. Simple random sampling can generally be carried out by drawing lots, shaking numbers or looking up a random number table. This sampling method is more suitable for small differences between total units. Implementation steps: (1), obtain the list of total units, that is, all the investigated objects; (2), for the whole unit number; (3) Sampling by lottery and random number table.
Equidistant sampling. Isometric sampling is also called mechanical sampling or systematic sampling. This sampling method requires that all the units in the population are arranged according to space, time or some signs unrelated to the investigation, and then the sample units are extracted in turn at equal intervals. The sampling interval is equal to the quotient of the number of samples divided by the number of units in the population. This sampling method is more convenient when used in a large number of people under investigation. Implementation steps: (1), obtaining the whole sampling frame; (2) The number of queues in the whole unit; (3) calculating the sampling distance interval; (4) In the number of sampling distance intervals, randomly select a sample unit; (5) Take other sample units in turn according to the number of intervals.
Stratified sampling. Stratified sampling is also called classified sampling or type sampling. It is suitable for situations with large population and great differences. Firstly, the population units are classified and layered according to their differences or certain characteristics, and then sample units are randomly selected in each class or layer. Stratified sampling is actually a combination of scientific grouping or classification and randomness. Stratified sampling can be divided into equal ratio sampling and unequal ratio sampling. When the total type difference is too large, unequal ratio sampling can be used. In addition to stratification or classification,
Overall sampling. Whole sampling is to divide the whole unit into "groups" or "groups" according to certain standards, select "groups" or "groups" from them, and then combine the individuals contained in the extracted "groups" or "groups" as samples. All units in the extracted "group" or "group" are sample units, and finally the extracted "group" or "group" is used as a sample. However, the investigation within a "group" or "group" is a general survey, and the overall sampling can be divided into two types: one-stage sampling and phased sampling.