Mathematics compulsory course 3. According to the chapter catalogue of Compulsory Mathematics 3 in Senior High School published by People's Education Publishing House, the first chapter is about statistical sampling methods, including random sampling and equidistant sampling. Statistical sampling refers to a sampling method that has the following characteristics at the same time: randomly select samples and evaluate the results of samples by probability theory, while sampling methods that do not have the above two characteristics at the same time are non-statistical sampling.