Why should an experiment be controlled?

• A. To make the data look more impressive.
• B. To ensure that results are not skewed by unintended consequences of shifting conditions.
• C. To increase the speed of the experiment.
• D. To require larger sample sizes.

Answer: (B)

Controlling an experiment means keeping all variables except the one you’re testing the same across all groups. This prevents other factors from influencing the outcome, so any observed change can be attributed to the factor you’re examining. In other words, it prevents unintended shifts in conditions from skewing results.

That’s why the best choice says that controlling ensures results aren’t skewed by those unintended consequences of changing conditions. The other options miss the point: control isn’t about making data look impressive, speeding up the experiment, or forcing larger sample sizes.