According to the number of questions, the main questionnaire suggests that it depends on what kind of investigation it is. It is almost enough to select dozens of people in different stages of ordinary school investigation, and social investigation is a little more troublesome. According to the classification of questions, several people are investigated in each category.

Questionnaire, also known as questionnaire or inquiry form, is a printed version that systematically records the contents of the survey in the form of questions. Questionnaires can be forms, cards or bookkeeping. Designing a questionnaire is the key to inquiry and investigation. A perfect questionnaire must have two functions, that is, it can convey the questions to the interviewee and make the interviewee happy to answer them. To accomplish these two functions, the questionnaire design should follow certain principles and procedures and use certain skills.