Final answer:
The variable that is changed in the experimental group is the independent variable. This factor is actively manipulated to measure its effects on the dependent variable, while maintaining controlled variables constant to isolate the relationship between the independent and dependent variables.
Step-by-step explanation:
The factor that is changed in the experimental group is known as the independent variable. The independent variable is the one that is manipulated or controlled by the experimenter to investigate the effects on the dependent variable. In a controlled experiment, this is the only major difference between the experimental and control groups. For instance, if a scientist is testing the effect of a new drug on blood pressure, the drug itself is the independent variable. The scientisits alter the dosage of the drug to see how it affects the study outcomes, which in this case is the blood pressure of participants, making blood pressure the dependent variable.
Controlled variables, on the other hand, are those factors which are kept constant throughout the experiment to ensure that any changes in the dependent variable can only be attributed to the changes made in the independent variable.