Statistics/Displaying Data/Frequency Polygon
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A frequency polygon shows approximately the smooth curve that would describe a frequency distribution if the class intervals were made as small as possible and the number of observations were very large. The very common bell curve used to represent a normal distribution is an idealized, smoothed frequency polygon.
One way to form a frequency polygon is to connect the midpoints at the top of the bars of a histogram with line segments (or a smooth curve). Of course the midpoints themselves could easily be plotted without the histogram and be joined by line segments. Sometimes it is beneficial to show the histogram and frequency polygon together.
Unlike histograms, frequency polygons can be superimposed so as to compare several frequency distributions.
