Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What is the purpose of a control variable in an experiment?

1. To measure the primary outcome variable

2. To be manipulated for effects

3. To hold constant other factors

4. To serve as a baseline for comparison

The correct answer is: To hold constant other factors

The purpose of a control variable in an experiment is to hold constant other factors that could influence the outcome of the experiment. By keeping these variables unchanged, researchers can ensure that any observed effects can be attributed more confidently to the manipulation of the independent variable. This helps to eliminate confounding variables, which are factors other than the independent variable that might affect the dependent variable, leading to more accurate and reliable results. In contrast, measuring the primary outcome variable pertains to assessing the effects of the independent variable on the dependent variable, while manipulating for effects refers to the independent variable being changed intentionally to observe its impact. Serving as a baseline for comparison typically refers to a control group used in experiments, which helps determine the effect of the independent variable by providing a standard against which the experimental results can be compared. However, the control variable specifically pertains to maintaining consistency in certain conditions, making it essential for the integrity of the experimental design.