Frequency Polygon.

Frequency Polygon.

For an ungrouped distribution, the frequency  polygon is obtained  by , plotting points with abscissa as the variate  , values and the ordinate as the corresponding frequencies and joining the plotted points by means  of straight lines. For a grouped frequency distribution, the abscissa  of points are mid-values of the class intervals. For equal class intervals the  frequency polygon can be obtained by joining the middle Points of the upper sides of the adjacent the class intervals are rectangles of the histogram by means of straight lines. If of small width the polygon can be approximated by a smooth curve. The frequency curve can be obtained by drawing a smooth freehand curve through the vertices's of  the frequency polygon.