A frequency polygon is a simple way of representing quantitative data. It is usually used for ungrouped data (a histogram is more commonly used for grouped data).
It is a plot of points whose x-coordinate represents values that are observed and the y-coordinate is a count of the number of times the value was observed. These points are joined together using straight lines to form the frequency polygon.
Often the first point is joined to a point on the x-axis that is one unit before the x-coord of the first point, and the last point is joined to a point on the x-axis that is one unit after the x-coord of the last point to complete the polygon.
In order to plot the points on either the frequency polygon or curve, the mid values of the class intervals of the distribution are calculated. Then the frequencies with respect to the mid points are plotted. However in a frequency curve the points are joined by a smooth curve, where as in a frequency polygon the points are joined by straight lines. Apart from this major difference, a frequency polygon is a closed figure where as the frequency curve is not.
A frequency curve is a graph obtained by joining the points of a frequency polygon freehand smoothly.
For ungrouped data.
frequency polygon
The definition of a irregular polygon is any polygon that is not a regular polygon.
This is called a frequency polygon.
In a Frequency Polygon, a line graph is drawn by joining all the midpoints of the top of the bars of a histogram. A frequency polygon gives the idea about the shape of the data distribution. The two end points of a frequency polygon always lie on the x-axis.
In order to plot the points on either the frequency polygon or curve, the mid values of the class intervals of the distribution are calculated. Then the frequencies with respect to the mid points are plotted. However in a frequency curve the points are joined by a smooth curve, where as in a frequency polygon the points are joined by straight lines. Apart from this major difference, a frequency polygon is a closed figure where as the frequency curve is not.
A frequency polygon is not very effective in displaying group data when the class sizes are not the same.
A cumulative frequency polygon has straight lines connecting the points. A normal cumulative frequency diagram uses a smooth curve to join the points.
By its very nature, measuring cumulative frequency on either axis of a graph will produce a continuing line on the opposite axis. Therefore, it is impossible to construct a closed frequency polygon when dealing with cumulative frequency.
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A frequency curve is a graph obtained by joining the points of a frequency polygon freehand smoothly.
Identify the midpoint of the top of each bar of the frequency diagram. Join these together and they will form a frequency polygon. Sometimes the polygon is extended down to the horizontal axis to where the midpoints of the bar before the first bar would have been and where the bar after the last bar would have been.
Frequency polygons are graphical devices used for understanding the shapes of distribution.
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