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

The primary purpose of a control in an experiment is to provide a standard for comparison. A control group or condition is established so that researchers can determine the effect of the independent variable by comparing the experimental outcomes with those of the control. This allows for a clearer understanding of how the variables interact and affects the results of the experiment.

In any scientific investigation, ensuring that results can be attributed to the variable being tested is crucial. By having a control, which remains constant while the experiment manipulates other factors, it's possible to highlight any changes in the dependent variable directly linked to the experimental conditions. This enhances the validity of the results and helps in isolating cause-and-effect relationships.

The other options, such as making the experiment quicker, randomizing results, or increasing sample size, do not fundamentally relate to the core function of a control. Instead, they pertain to different aspects of experimental design.