June 13th, 2013
This is a simple visualization of the Arithmetic mean (aka, the average.) Click and drag the balls around and watch the mean (the larger yellow ball) update.
The mean is often used to describe the central tendency of a set of data values. It's one possible answer to the question "what is a typical value for the data set?"
It's important to remember that the mean is not a
robust statistic meaning that outliers will have a large effect on the mean. You can see this in the visualization by adding several balls to one side in a concentrated area and then adding a single ball to the opposite side.
Note that the size of the balls are meaningless in the visualization. They're only large enough to be clicked on. The mean ball has twice the radius of the others only so you can still see it when the other balls are in front of it.
You can find a copy of the code to this visualization here: http://bl.ocks.org/vicapow/5778069