Observational Study

Observational studies are used in scientific research to draw inferences from a population or sample where the independent variable cannot be controlled due to ethical concerns or logistical constraints. This type of research is commonly used in fields such as epidemiology, psychology, and sociology, where it is often impossible or unethical to manipulate variables. For example, the Souza et al. study (1) is observational because knee pain cannot be randomly assigned.  This study compared individuals with knee pain to "matched-controls" without knee pain.