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

The purpose of a control group in an experiment is to provide a baseline for comparison. This allows researchers to determine the effect of the independent variable by comparing the results of the experimental group, which is exposed to that variable, with the control group, which is kept under standard conditions without the independent variable's influence. By having a control group, it becomes possible to assess whether any observed changes in the dependent variable can be attributed specifically to the manipulation of the independent variable or if they are due to other factors.

This is crucial for establishing a cause-and-effect relationship, as the control group helps to isolate the effects of the independent variable from other variables or influences that could affect the outcome of the experiment. In contrast, the other options involve different aspects of the experimental design. Manipulating the independent variable pertains to how experiments are structured, measuring the dependent variable relates to data collection, and ensuring randomness is about sampling methods, all of which are important but do not define the specific role of the control group.