The Experimental Method

The data, theories, and laws of hearing are derived from experiments. In order to understand hearing better, having some understanding of the experimental method is useful. The empirical scientific method involves the manipulation of one variable (the independent variable) to test for its effect on another variable (the dependent variable). That is, how does the dependent variable change as a function of changes in the independent variable? The experimental result is stated in terms of the functional relationship between the independent and dependent variable. Often, other variables change along with (covary) changes in the independent variable. Thus, these other variables may lead to the change in the dependent variable. If this happens, the other variables confound the relationship between the independent and dependent variable, and as a result these other variables are called confounding variables. Different experimental methods are used to control for confounding variables, so that a direct relationship between the independent and dependent variables can be established.

In the example provided below, the slope of an incline is changed and the time in takes the ball to roll down the incline is measured. By clicking on each incline, you will see the rolling ball and you will be given the incline slope (the ratio of the height to the width of the incline) and the time (seconds) it took for the ball to roll down the incline.

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With these measures answer the following questions. The answers are provided by going to the answer page.

1. What are the dependent and independent variables in the ball rolling experiment?
   
2. What is a potential confounding variable (or variables)?
   
3. Provide a Table of the results showing how the time for the ball to roll down the incline changed with incline slope.
   
4. Provide a Plot of the data of the Table for question 3. In a plot of experimental results the values of the independent variable are plotted along the horizontal or x-axis and the values of the dependent variable are plotted along the vertical or y-axis.
   
5. What is the functional relationship between the independent and dependent variable? You can express the relationship in words, but a linear equation can also be used to describe the relationship. A linear relationship defines a line and it has the form of DV = m(IV) + b, where DV is the dependent variable, IV is the independent variable, "m" is a constant representing the slope of the line, and "b" is a another constant.
   
6. How might the experiment be redesigned to control for the influence of the confounding variable(s) on the dependent variable?