There is Qiu Dazheng from Gaobei Middle School in the second volume of the current textbook Mathematics for Grade Eight published by Beijing Normal University. The fifth chapter is "data collection and arrangement". The statistical knowledge involved was originally the last chapter of the ninth grade study in the previous People's Education Press, but now the textbooks break it down into different academic years in order to achieve the goal of gradual progress. We all know that the basis of statistics is to collect data, and the premise of collecting data is to choose appropriate investigation methods. Therefore, how to choose an appropriate survey method is the premise and element for the smooth data collation and description. There are two ways to collect data: comprehensive survey and sampling survey. The object of comprehensive investigation is to understand the comprehensive and accurate situation, and the object of sampling investigation is to understand the general situation. Specifically, when the number of objects we know is small and the investigation is not difficult, we can adopt the comprehensive investigation method; On the other hand, if the number of individuals surveyed is large, or it is impossible to conduct a comprehensive survey due to some objective conditions, then there is another possibility that the survey is destructive to some extent and it is not allowed to conduct a comprehensive survey, so sampling survey should be adopted. In the sampling survey, the selection of samples should follow three principles: first, the number of respondents should not be too small, but should be extensive; Second, the respondents should be randomly selected and representative; Third, the survey data must be true and reliable, with a high degree of authenticity, as illustrated by the following examples. First, is it suitable for a comprehensive investigation? For example 1, the following surveys need to adopt a comprehensive survey method: (1) TV stations investigate the ratings of "Focus Interview" being broadcast. B the quality inspection department investigates the service life of a batch of light bulbs. C. A middle school investigated the uniform work clothes made by canteen workers. Investigation of soil erosion in the upper reaches of the Yellow River by environmental protection department. Analysis: Because the number of employees in the canteen is limited, and each employee must have an accurate size to cut clothes that fit him, everyone must undergo accurate measurement and be suitable for comprehensive investigation. Options A, B and D cannot be implemented due to a lot of investigations and some objective conditions, so C is chosen. Second, is it suitable for sampling survey? Example: To understand the temperature changes in a city, the most reliable of the following observation methods is () A. Randomly select 30 days for observation. B, random sampling for a month for continuous observation. C. Randomly select one month for continuous observation throughout the year. D, a week is randomly selected throughout the year for continuous observation. Analysis: It is obvious that A and B are not universally representative, so they are not suitable for investigating the temperature changes in a city all year round. The sample size in D is too small to reflect the temperature change in this city every quarter, so D is not suitable. The most suitable is C. 3. Correctly distinguish between comprehensive survey and sampling survey. The following statement is correct: (a) Only through comprehensive investigation can the overall characteristics be obtained. Sampling survey is the only way to get data. C, comprehensive survey is much more convenient than sampling survey. D, sampling survey samples should be random. Analysis: judge according to what you have learned, so choose D. Summary: What kind of investigation method to choose should be determined according to the actual situation of the analysis problem and the characteristics of various investigation methods. Generally speaking, the number of individuals in the survey is small, and a comprehensive survey is preferred; When the number of individuals in the survey population is large and cannot be implemented smoothly, sampling survey should be preferred. Students should master the basic knowledge of textbooks in their study and make appropriate choices according to the actual situation when applying them in practice.