There is significant potential for error in long production processes that consist of sequential stages, each of which is heavily dependent on the previous stage, such as the SER (Scoring, Equating, and Reporting) process. Quality control procedures are required in order to monitor this process and to reduce the number of mistakes to a minimum. In the context of this module, quality control is a formal systematic process designed to ensure that expected quality standards are achieved during scoring, equating, and reporting of test scores. The module divides the SER process into 11 steps. For each step, possible mistakes that might occur are listed, followed by examples and quality control procedures for avoiding, detecting, or dealing with these mistakes. Most of the listed quality control procedures are also relevant for Internet-delivered and scored testing. Lessons from other industries are also discussed. The motto of this module is: There is a reason for every mistake. If you can identify the mistake, you can identify the reason it happened and prevent it from recurring.