Which statement best describes the roles of independent and dependent variables in an experiment?

• A. Independent variable is deliberately changed; dependent variable is the outcome measured.
• B. Dependent variable is the outcome measured.
• C. Independent variable is the outcome; dependent variable is the tool used.
• D. Independent variable is random; dependent variable is fixed.

Answer: (A)

In experiments, the key idea is about manipulating cause and observing effect. The variable you deliberately change is the independent variable, and the variable you measure to see the result is the dependent variable. This setup lets you test whether changing the independent variable leads to changes in the dependent variable, indicating a possible causal relationship. For example, if you test whether study time affects exam scores, study time is the independent variable (you change it), and exam score is the dependent variable (you measure it). The other statements misrepresent roles: the dependent variable isn’t a tool, the independent variable isn’t the outcome, and neither variable is inherently random or fixed—the randomization used in experiments pertains to assigning participants, not a property of the variables themselves.