When an independent variable would endanger a human participant's health, we must conduct the research by comparing groups that already have differing degrees of the variable of interest. these are known as experiments?

The answer is quasi-experiment. The quasi-experiments are engaged when the researcher is interested in independent variables that cannot be randomly assigned. Typically this occurs when the independent variable in question is something that is an innate characteristic of the accomplices involved. The differences among true experiments and quasi-experiments are in a true experiment the participants are casually assigned to either the treatment or the control group, while they are not assigned randomly in a quasi-experiment.

True. r u cheating on a test. bro not cool.