Why does a scientist include a control in the design of an experiment?

A scientist includes a control in an experiment to establish a baseline for comparison, allowing them to determine the effect of the independent variable on the dependent variable. The control helps to isolate the specific impact of the experimental treatment by ensuring that other variables remain constant. This enhances the reliability and validity of the results, making it easier to draw accurate conclusions. Without a control, it becomes challenging to ascertain whether observed changes are due to the experimental conditions or other external factors.