A frequency polygon serves the same purpose as a frequency histogram. The frequency polygon is drawn by connecting the points, representing frequencies, located above the scores. Note that a polygon is completed by extending it to the abscissa one value below the lowest score and one value above the highest score in the distribution. Frequency polygons communicate the same information as a histogram and are not particularly popular in psychological reports.

A frequency polygon permits the plotting of more than one distribution on the same set of axes. Plotting more than one frequency histogram on a set of axes might create a confusing graph. If more than one frequency polygon is plotted on a set of axes, they should be distinguished from one another. This can be done by drawing a different kind of line for each polygon (perhaps a solid line for one and a broken line for the other), drawing the lines in different colors (perhaps red for one polygon and blue for the other), or representing the points above the scores with geometric shapes (perhaps a circle for one polygon and a triangle for the other). Using different colored bars for different variables represented in the same histogram could accomplish much the same thing.