What does a variable represent in an experiment?

In the context of an experiment, a variable represents the factor that is being changed or manipulated to observe its effect. This change is critical for testing hypotheses and understanding cause-and-effect relationships. By altering a variable, researchers can identify how this change influences other conditions or outcomes in the experiment.

For instance, in a scientific study investigating the impact of different fertilizers on plant growth, the type or amount of fertilizer used would be considered the variable. By adjusting this factor, researchers can collect data on how it affects the growth of the plants, thus allowing conclusions to be drawn about the effectiveness of various fertilizers.

To reinforce the understanding of what a variable is, it can be contrasted with the other choices. A constant factor refers to elements of the experiment that are kept the same to ensure that the results are due to the variable being tested, while the factor that remains unchanged typically describes what a constant does in an experiment. Lastly, the outcome of the experiment relates to the results gathered after the variable has been manipulated, but it does not itself constitute the variable being tested.