How many copies of the questionnaire are appropriate?

Generally speaking, when determining the sample size, we need to consider the purpose, nature and accuracy requirements of the survey. And the feasibility of actual operation and the affordability of funds. According to the survey experience, a survey with strict requirements on market potential and inference requires a relatively large sample size, while a survey with average advertising effect is not very different from other people or has not strict requirements on sample size, and the sample size can be relatively small. In fact, determining the sample size is a complex problem, that is, there must be qualitative and quantitative considerations; From a qualitative point of view, the importance of decision-making, the nature of investigation, the nature of data analysis, resources and sampling methods all determine the sample size. But this can only determine the sample size in principle. The specific determination of sample size also needs to be considered from a quantitative point of view.

In other words, the more complex the problem, the greater the difference and the larger the sample size; The higher the required accuracy, the higher the reasoning requirements and the larger the sample size; At the same time, the larger the population, the larger the sample size, but the increase presents a certain logarithmic feature, not a linear relationship; The problem of sampling method determines the value of design effect. If we set the value of simple random sampling design effect to1; Because the sampling efficiency of stratified sampling is higher than that of simple random sampling, its design effect value is less than 1. Proper stratified sampling will reduce the intra-layer sample difference, and the smaller the intra-layer difference, the larger the range where the design effect is less than 1. Because the efficiency of multi-stage sampling is lower than that of simple random sampling, and the design effect value is greater than 1, the complexity of sampling survey method determines its sample size.

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