The independent variable is the only factor that a scientist

varies for different groups in an experiment.

measures in an experiment.

keeps constant for each group in an experiment.

does not change throughout an experiment.

The correct answer is option (A) varies for different groups in an experiment.

An experiment conducted by a scientist always has a dependent and a independent variable. A dependent variable in an experiment is a variable which is being tested and measured. An independent variable in an experiment is the variable that is changed or controlled in the scientific experiment to test the effects of the dependent variable. An independent variable always changes to check its effect on the dependent variable. For example, if the growth of two plants are being tested with the application of a  fertilizer to one plant and not to the other, the growth of the plant is the dependent variable and the fertilizer becomes the independent variable which changes for both the plants throughout the experiment.