Question

why is it important to have a control group in an experimental investigation? to show what happens when the dependent variable is not changed to see how the dependent variable changes the independent variable to compare the results when the independent variable is not involved to allow the researchers to change the dependent variable as they wish

Explanation:

In an experiment, the independent variable is manipulated in the experimental group. The control group has no such manipulation of the independent variable. By comparing the two groups, researchers can determine the effect of the independent variable.

Answer:

to compare the results when the independent variable is not involved