The Quality Assurance and Control Plan

Quality assurance relates to all actions taken to ensure respect for general epidemiological principles. Consequently, quality assurance includes many aspects of study design and conduct, including quality control activities. Quality control (QC) relates to the monitoring and documentation of the validity and efficiency of study procedures and, if necessary, actions for adapting procedures or improving adherence to them. Ultimately, the purpose of QC is to achieve optimal data quality. In this chapter we outline QC methods and tools, prime among them being the monitoring of measurement error and other factors that could bias the statistical results of a study.