Take a look at all the scores in your class from the dice game. What is the range of scores? What does this tell you about the scores as a whole? Your score?

The range provides important information about the data set, but it really only takes into account two data points. It's kind of like taking a vacation where only the departure and the destination are important and the trip itself is ignored... but sometimes (usually) we want to include something about the points in between.

In order to do this, we need to relate the points to some fixed point. We have two good choices, the median and the mean. If you recall, the median doesn't really take into account the "weight" of each data point, whereas the mean does. So, let's go with the mean as our point of relation (if you like, try using the median and discuss its benefits and drawbacks).

The easiest way to compare each point to the mean is to subtract the mean data point from the observed data point. Because some points are above the mean and some below the mean, you will get both positive and negative numbers. Try adding those "deviation scores" up and see what you get.