Final answer:
The best-suited method to determine cause-and-effect relationships is an experiment, as it allows researchers to manipulate and control variables to directly observe effects, unlike correlational or observational studies which can only establish correlations.
Step-by-step explanation:
To determine cause-and-effect relationships, the best-suited method is an experiment. This approach allows researchers to manipulate one variable (the independent variable) while controlling other variables to observe the effects on a second variable (the dependent variable). In contrast, observational studies, such as naturalistic observation and correlational studies, can generally establish correlation but not causation. Correlations may show that variables are related, but without experimental manipulation, it's impossible to conclude that one variable causes the changes in another.
For example, in an experimental study investigating whether aspirin reduces the risk of heart attacks, participants might be randomly assigned to an aspirin group or a placebo group, allowing for a direct comparison and the ability to draw causal inferences. On the other hand, a correlational study might find that people who exercise more are less likely to develop heart disease, but because this is not an experiment, these findings cannot definitively conclude that exercise causes a reduction in heart disease.