Quality problems main arise from five aspects: unqualified interviewers, interviewers lack of understanding of questionnaire, interviewees criteria, interviewing process, and filling questionnaire.    CPResearch has already accumulated rich experiences to deal with these problems. There is a separate QC team in CPResearch, however this team always closely work into each stage of data collection with DC supervisors so that their findings and suggestions could be better executed. 　 　 　 Interviewer Management 　 Separate supervisor is responsible for interviewer recruitment, interview skill training, pilot interview, and qualification examination. CPResearch will sign at least one-year contract with qualified interviewers. CPResearch usually has more than 500 of face-to-face and CATI interviewers. Project Briefing and Interviewing Control 　 Based on interviewers' major (college students) or experiences, they will be selected as interviewers of different project. After briefing, they will mock each other, then do pilot interview, and experienced supervisors will accompany new interviewers to do several interviews. After finishing 5% interviews, supervisors will meet with all interviewers together to discuss with them about current problems they are facing. Back Check 　 Interviewee criteria, interviewing process, and questionnaire filling are always the sources of quality problem. CPResearch usually provides 25%-50% of back check for experienced interviewers, and 100% for new interviewers. Sampling Frame Management 　 CPResearch has its own databases or panels for sampling. CPResearch keeps yearly update these databases.