Final answer:
Experimental investigations provide the capacity to control variables by manipulating an independent variable to observe effects on a dependent variable, while keeping other variables constant.
Step-by-step explanation:
Experimental investigations allow for the control of variables. This type of study, often referred to as a controlled experiment, involves manipulating one variable (the independent variable) to determine if changes occur in another variable (dependent variable). By keeping other variables constant (control variables), and often incorporating a control group which does not receive the experimental manipulation, researchers can establish a cause-and-effect relationship between the variables being studied. This setup minimizes the influence of external factors and increases the reliability of the results. If changes in the dependent variable are observed, these can often be attributed to the manipulation of the independent variable, thus supporting the hypothesis being tested.