What is the purpose of a controlled experiment?

The purpose of a controlled experiment is to test a hypothesis while keeping all variables constant except one. This approach allows researchers to draw a clear cause-and-effect relationship between the independent variable (the one being changed) and the dependent variable (the one being measured). By controlling all other variables, the experimenter minimizes the influence of external factors, which ensures that any observed changes in the dependent variable can be attributed directly to the manipulation of the independent variable. This method is fundamental in scientific research because it enhances the reliability and validity of the results, allowing for more accurate conclusions to be drawn about the hypothesis being tested.

In contrast, measuring the effects of all variables would complicate the experiment and make it difficult to determine what specifically caused any observed changes. Observing natural phenomena without interference does not allow for manipulation of variables and thus wouldn't test a hypothesis effectively. Creating random conditions for experimentation could lead to inconsistent results, as it introduces variability that does not support the systematic testing of hypotheses.