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

A control group serves a crucial role in scientific experiments by providing a benchmark against which the results of the experimental group can be compared. By maintaining all conditions similar to those of the experimental group except for the variable being tested, the control group allows researchers to determine whether the changes observed in the experimental group are due to the independent variable or other external factors.

When an experimental group is subjected to specific conditions to test the effects of a variable, the control group remains unchanged and does not receive the treatment. This setup helps ensure that any observed differences can be attributed to the manipulation of the independent variable, thus lending credibility to the conclusions drawn from the experiment.

The other options imply functions that are not accurate for the role of a control group. A control group does not test all variables or manipulate experimental conditions; rather, it preserves the standard conditions for comparison. Furthermore, isolating the independent variable relates more to the design of the experiment itself rather than the specific function of the control group.