Count the frequency of different values of a group of data, or the frequency of data falling into a specified area, in order to understand the way of data distribution. Through frequency analysis, we can reflect to some extent whether the samples are generally representative and whether there is systematic deviation in sampling, which proves the representativeness and credibility of future analysis of related issues.

2. Descriptive statistics:

Statistically describe the relevant data of all variables in the survey population, including the centralized trend and discrete trend of the data.

3. Exploratory analysis:

Normality test is used to test whether the data conforms to the normal distribution, and some algorithms require the data to conform to the normal distribution (such as single sample t test, independent sample t test, etc.). ).