Final answer:
Natural/quasi-experiments in health care research, such as studies on smoking bans and lung cancer, rely on observational studies rather than manipulating variables, due to ethical and practical considerations. Case-control studies, like Doll and Hill's research on smoking, typically compare different exposure groups to evaluate health outcomes.
Step-by-step explanation:
An example of a natural/quasi-experiment in the context of health care would be studying the impact of a smoking ban in public places on respiratory health outcomes. In such instances, manipulating variables to test outcomes is not feasible, practical, or ethical. Instead of creating an experimental situation, researchers utilize observational studies to compare groups with differing exposures to a variable of interest, such as smoking, to evaluate the association with health outcomes like lung cancer or cardiovascular disease.
A classic case that underscores this approach would be the research by Doll and Hill, who conducted a case-control study on smoking and lung cancer. Through interviewing lung cancer patients (cases) and people without lung cancer (controls) and comparing their past smoking habits, a strong association was found between smoking behavior and lung cancer status. Such studies are not only more ethical but often more practical than experimental studies when it comes to public health research.