Topic overview

Start with the big picture

Study design and analysis offer complementary opportunities to address bias and confounding. Design-stage decisions can help reduce the likelihood that systematic errors affect a study, while analysis-stage approaches can account for relevant differences in the data. These strategies do not make every study limitation disappear; rather, they help researchers consider how study methods shape the findings. This introduction frames control as a connected process: anticipate potential problems before data collection, then evaluate and address them during analysis. The deeper lesson develops this framework and explains how these considerations support cautious interpretation of epidemiological evidence.