Like histograms, frequency polygons display the frequency or ‘counts’ of a measure across each of its possible values or intervals. Unlike histograms, frequency polygons present these data as a line of connected frequency values (ie a line graph), rather than individual bars.

Polygons are used instead of histograms when the measure has a large number of intervals and you want to convey a message about the shape of the overall distribution, rather than individual data points. Polygons are also useful for presenting multiple distributions (ie a distribution for multiple groups) on the same graph: