What is the purpose of a controlled experiment?

• A. To observe results.
• B. To form a hypothesis.
• C. To measure conclusions.
• D. To test variables while keeping other variables constant.

Answer: (D)

A controlled experiment is designed to test how one variable affects an outcome by keeping all other factors the same. By changing only the independent variable and holding constant every other condition, you can see if the observed change in the dependent variable truly comes from that factor. This setup reduces the influence of other variables, making results reliable and repeatable. Observing results, forming a hypothesis, or drawing conclusions are important parts of science, but the main purpose of a controlled experiment is to isolate the effect of a single variable by keeping others constant.