Which is NOT a typical data collection method in observational studies?

In the context of observational studies, randomized controlled trials (RCTs) are distinctly different and do not align with the typical data collection methods used in observational research. Observational studies aim to observe and record data without manipulating the study variables or interventions, which is central to their design.

Surveys or questionnaires, direct observation, and medical record review are all common data collection methods in observational studies. Surveys and questionnaires allow researchers to gather information directly from participants, capturing their responses and perspectives. Direct observation involves watching subjects in their natural environment to gather data on behaviors or events without interference. Medical record review allows researchers to access existing data from patients' health records, providing insights into outcomes and trends over time based on real-world evidence.

In contrast, randomized controlled trials involve the random assignment of participants to different groups to receive various interventions, distinguishing them from observational methodologies that do not involve such manipulation. Therefore, identifying randomized controlled trials as not a typical data collection method in observational studies emphasizes the fundamental difference in study design between observational studies and RCTs.