Which research method allows for the least ambiguous conclusions regarding causality?

Question

Quizplus · Accepted Answer

Experimental research is the only method that can establish causality with the use of controlled variables, random assignment, and manipulation of the independent variable. Correlational research can only establish associations between variables, and quasi/natural and naturalistic observation lack experimental control and cannot demonstrate causal relationships.

Which Research Method Allows for the Least Ambiguous Conclusions Regarding