How to Select and Report the Appropriate Study Design

A clear understanding of study designs is essential for planning research and critically evaluating evidence. The choice of design depends on the research question, with multiple designs often suitable for a single question. Misapplication or misreporting of study designs can threaten validity and mislead readers. This manuscript provides an overview of common quantitative study designs, including observational and experimental studies. Common reporting errors include omitting the study design, incorrect labelling, inappropriate causal claims, failure to identify confounders, and omitting details of randomisation and allocation concealment.