What characterizes a controlled experiment?

A controlled experiment is characterized by the practice of keeping all conditions constant except for one variable. This approach ensures that any observed effects on the dependent variable can be confidently attributed to changes in the independent variable that is being tested. By controlling all other factors, researchers minimize the potential influence of extraneous variables, allowing for a clear relationship to be established between the variable of interest and the outcome.

This method is fundamental to scientific inquiry, as it helps to establish cause-and-effect relationships. For instance, if you're testing the effect of a new drug on blood pressure, you would keep factors like diet, exercise, and age constant among participants while varying only the dosage of the drug. This level of control enhances the reliability and validity of the findings.

In contrast, testing multiple variables simultaneously introduces confounding factors, making it difficult to pinpoint which variable is responsible for any changes observed. Allowing random variation in results does not support the systematic investigation of a hypothesis, as it introduces noise rather than clarity. Finally, relying on observational data rather than experimental data typically lacks the level of control necessary to establish causal relationships, as the researcher cannot manipulate variables.