What's the difference between simple random sampling and systematic sampling?

Random sampling is a survey method that selects some units from all survey units according to the principle of randomness and investigates and infers the whole population according to the survey results.

The concept of simple random sampling

Generally speaking, assuming that a population contains n individuals, if a sample is extracted from it one by one, and the probability of each individual being extracted is equal, then such a sampling method is called simple random sampling.

Simple random sampling requires that the total number of samples sampled, n, is limited.

The numb n of simple random samples is less than or equal to that numb n of the sample population.

Extract simple random samples from the population one by one.

Simple random sampling is a kind of sampling that cannot be put back.

The probability of each individual being systematically sampled is n/n.