What is repeated sampling? What is non-repeated sampling?

Repeated sampling refers to the method of taking any sample and then putting it back into the group to participate in the next sampling. It is also called back sampling.

Non-repeated sampling In the process of sampling from the population unit, any sampled sample unit will not be put back into the population to participate in the next sampling method. It is also called non-return sampling.

Method characteristics

When the non-repeated sampling method is adopted, the number of units in the population decreases gradually during the sampling process, and the probability of each unit being drawn in the population is different in turn. When the number of units in the group is small, the probability of each unit being drawn in the group is quite different, and vice versa. Non-repeated sampling method is simple and feasible.

When repeated sampling is adopted, the whole unit always remains the same, and the chances of each unit being extracted are completely equal. However, in practice, sampling samples are often destroyed in the process of inspection, such as product quality inspection, so it is impossible to put them back into the population. Usually, repeated sampling is adopted only when objective conditions do not allow it. When the proportion of samples in the population is small, the error of repeated sampling is almost equal to that of non-repeated sampling.