How to determine the sample size of the questionnaire survey?

The sample size of the questionnaire is the number of units contained in the sample, that is, the number of individuals sampled. The sample size will affect the sampling error, the time required for investigation, the cost required for investigation and some information of the members of the investigation team. So how to determine the sample size, mainly has the following factors.

First of all, the predicted value should have certain accuracy. Because the sampling error will directly affect the accuracy of the estimated value.

The second is the variation of the overall indicators. This will affect the accuracy of the response rate, thus affecting the sample size. In the process of calculating samples, we should also consider the following important links.

First of all, in order to ensure the accuracy of sampling rate, sampling inference must be done well to make it credible;

The second is to determine the overall variation degree according to the variance. If the variance is large, draw more points; if the variance is small, draw less points.

Third, the number of samples should be determined according to variance;

Fourth, the number of samples should be determined according to the funding situation, including the expenses of investigators, investigation channels and questionnaires.

Thirdly, the sample size is closely related to the estimated value. With the increase of the sample size, the accuracy of the estimated value will also improve.

After determining the sample, the calculation of sample size is a key issue, which requires a scientific formula, which is professional, so we will not introduce the formula in detail here. Generally speaking, the sample size depends on the number of estimation domains.

In short, the determination of sample size should follow the principle of one person, that is, the interaction between accuracy and cost, and the cost must have the highest accuracy and accuracy and the lowest cost.