In an experiment, which statement correctly identifies the roles of the independent and dependent variables?

• A. The dependent variable is changed by the researcher; the independent variable responds
• B. The dependent variable is measured before manipulation; the independent variable is changed
• C. The independent variable is changed by the researcher; the dependent variable depends on it
• D. They are both constants

Answer: (C)

In experiments, you deliberately change one factor to see its effect on another. The factor you actively manipulate is the independent variable, and the factor you measure to observe the outcome is the dependent variable. So the best statement is that the independent variable is changed by the researcher and the dependent variable depends on it, because that captures the causal relationship you’re testing: changing the input leads to changes in the output.

The other ideas don’t fit the standard setup. Measuring the dependent variable before manipulation isn’t how you demonstrate cause and effect in a controlled experiment, since you’re interested in how the change in the input produces a response in the output. The idea that both variables are constants contradicts the whole purpose of an experiment, which is to observe how altering one variable influences another.