There are two different activities below. The point of these activities is to demonstrate that the mean is a balance point. When the fulcrum is lined up over the number that corresponds to the number in the box labeled "mean" then the beam will balance. The median is the value in the middle of the ordered data set. The mode is the number of boxes that appears most often. To operate both activities, drag the fulcrum along the base. In the first activity, the beam will change continuously as you drag the fulcrum. In the second activity, the beam will appear to move to a balanced state as soon as you start moving the fulcrum. Only after releasing the fulcrum will the beam be redrawn. You are able to drag the fulcrum by clicking on it and then by moving the mouse, while continuing to hold down the mouse button. Just release the mouse button to release control of the fulcrum.

Please, note that the beam is just a symbolic object to allow you to
visualize the concept better. It is a weightless object that does not
figure into any of the calculations. To change the configuration of
blocks in either activity, click on the reset button.
To end the lesson and return to the main menu, click on the browser's
"back" button.

>From the above activity, we found that the mean is precisely that point
that balanced the total of negative deviations with the total of the
positive deviations. Now, in this activity, you are asked to (intelligently)
guess at where the mean might be.