6.3.2 Generation and correction of doubt, quality control(QC) and database shutdown: After completing data input and comparison, data administrators will verify the reliability, integrity and accuracy of data according to requirements of clinical trial scheme. If he finds loss of content or logic contradiction or filling in wrong or uncertain data, clinical monitors will send it to clinical trial centers in the form of data question table (DQF). Researchers will give answers to questions as soon as possible and reply. Data administrators will modify, confirm and correct data according to researchers' answers. After solving all of problems, quality control personnels will check the quality of database according to QC plan. Then he will close the database after check.