(1) In the repeated sampling mode, n is the sample size, d is the sampling error range, and σ is the standard deviation, generally 0.5.

Calculation formula of variable population repeated sampling;

Attribute population repeated sampling:

(2) In the non-repetitive sampling mode:

Calculation formula of variable population non-repeated sampling;

Non-repeated sampling of attribute population:

Extended data

The significance of reasonably determining the sample size;

1, the sample size is too large, which will increase the investigation workload and waste manpower, material resources, financial resources and time;

2. If the sample size is too small, the sample is not representative enough to the whole population, and it is difficult to ensure the accuracy and reliability of the calculation results;

3. The determination of sample size is scientific and reasonable. On the one hand, at a given survey cost, the sampling error can be as small as possible to ensure the accuracy and reliability of calculation; On the other hand, given the accuracy and reliability, the investigation cost can be as small as possible to ensure the maximum effect of sampling inference.