StudienDesign

Studiendesign, or study design, refers to the overall plan that governs how a study is conducted to answer a research question. It specifies the study population, sampling method, timing of measurements, data collection procedures, and the variables to be observed, as well as the planned analyses. The design shapes the credibility of the results and the ability to draw conclusions about cause and effect.

The main design categories are experimental and observational. Experimental designs involve deliberate manipulation of an exposure or intervention and, most notably, random assignment of participants, as in randomized controlled trials (RCTs). Quasi-experimental designs mimic randomization but lack it, using natural groups or stepped-wedge implementations. Observational designs do not assign interventions and include cross-sectional studies (a single time point), cohort studies (a group followed over time to assess outcomes), and case-control studies (comparing past exposures between cases and controls). Longitudinal designs track participants over time, while cross-sectional designs provide a snapshot at one moment.

Quality considerations in studiendesign include internal validity (the extent to which observed effects are attributable to the studied exposure rather than confounding), external validity (generalizability), and the reliability and validity of measurement instruments. Bias and confounding must be addressed through design choices and analytical methods. Adequate sample size and power calculations, ethical considerations, preregistration, and transparent reporting using standardized checklists contribute to the rigor and reproducibility of a study.