Methods: Draw lots, random number table.
Conditions of use: the number of samples is small and the overall heterogeneity is small.
Simple random sampling method is based on the principle of randomness, which directly extracts several units from all N units as samples. It ensures that every object in the group has the same possibility of being extracted, and requires them to be independent.
Advantages: simple, easy to operate, convenient for error calculation and strong representativeness.
Disadvantages: when the sample size is small, there may be deviations, which will affect the representativeness of the sample.
For example, a school * * * has 1 000 students. Each student was numbered from 65,438+0 to 65,438+0,000, and the numbers were randomly selected by lottery, and 65,438+0,000 students were selected.