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Sampling survey is an incomplete survey, which is a survey method to select a part from all the respondents and estimate and infer all the respondents. Its purpose is to obtain information reflecting the overall situation, so it can also play a role in reflecting the overall situation. Sampling methods can be divided into two categories: probabilistic sampling and non-probabilistic sampling. Probabilistic sampling is based on the principles of probability theory and mathematical statistics, selecting samples from the investigated population, quantitatively estimating and inferring some characteristics of the population, so that possible errors can be controlled in a probabilistic sense. In China, it is customary to call probability sampling a sampling survey.
First, the characteristics of sampling survey
Sampling survey has the following three outstanding characteristics: 1, sampling according to the principle of randomness;
2. Every unit in the group has a certain probability of being drawn;
3. A certain probability can be used to ensure that the error is controlled within the specified range.
Two. Several main commonly used nouns in the sample survey, which mainly include:
1, the whole refers to all the objects to be studied. It is a collection of all disciplines to be investigated according to a certain research purpose, and the disciplines that constitute the whole are called the whole unit.
2. The sample sample is a part of the whole, and it is a collection selected from the whole by a part of the whole unit according to certain procedures.
3. Sampling box Sampling box refers to the box used to represent the population and select samples from it. Its specific manifestations mainly include the roster and maps of all units in the population. Sampling frame is in the basic position in sampling survey, and it is an indispensable part of sampling survey, which has a considerable influence on inferring the population.
4. Sampling ratio Sampling ratio refers to the ratio of the number of units in the sample to the total number of units in the sample. For the sampling survey, the representativeness of the sample and the authenticity of the estimated value finally calculated by the sampling survey depend on the quality of the sampling frame first.
5. Confidence confidence is also called reliability, or confidence level and confidence coefficient, that is, when sampling to estimate the overall parameters, its conclusion is always uncertain because of the randomness of the samples. So a probability statement method is adopted, that is, the interval estimation method in mathematical statistics, that is, within a certain allowable error range, what is the corresponding probability between the estimated value and the overall parameters? This corresponding probability is called confidence.
6. Sampling error In the sampling market survey, samples are usually used to estimate a certain feature of the population.