An experimental study is the design that can determine a cause-and-effect relationship. In experimental studies, researchers manipulate one or more variables to observe the effect on another variable, allowing for conclusions about causation. Randomized studies are a subset of experimental studies that enhance the validity of the findings by randomly assigning participants to different groups.
Observational studies and surveys, on the other hand, do not involve manipulation and can only identify associations, not direct cause-and-effect relationships.