A line graph servers a similar function to the histogram. When we graph frequencies, we can generate what is called a frequency polygon. Don’t let that “polygon” stuff throw you off. All we are talking about is a line graph that shows frequencies. If there is a good point to having that name, it is that we are reminded we are dealing with frequencies. We’ll be spending a lot of time talking about frequency polygons later. For now, just keep in mind that the height of the line (the vertical axis) tells us the frequency, and the position left to right along the horizontal axis (think of this one as a number line) tells us the score. Since most people tend to be average (unless you ask them), we find that the curve is highest in the middle where the mean is, and it trails off quickly to either side of the mean. Not every curve takes on this bell (think Liberty Bell) shape, but many things in nature do. The mathematical properties of the normal curve allow us to do some pretty cool things that make us look really smart. More on that later.
Last Modified: 02/18/2019