according to certain rules to extract a part of the object for investigation, and then

after the results of the survey to infer the overall situation of the method.

(2) Questionnaire survey method. That is, through the form of questionnaires,

investigation of the enterprise to understand the problem.

(3) telephone survey method. That is, the investigator through the phone

The phone to ask for each other's opinions.

(4) Personal visits and interview methods. That is, the investigator

by visiting the respondent, in person to the respondent to ask questions to

get information.