Frequency Polygon (Meaning and Explanation)

We explain what a frequency polygon is in statistics, what it is for and how to do it from a histogram and Excel.

What is a frequency polygon?

A frequency polygon is a graphical tool that is used from a frequency histogram (i.e., another type of graph that expresses frequencies using vertical columns). To do this, the different midpoints of the columns of the histogram are joined with a line, leaving no space between them, thus achieving a geometric shape or polygon.

With this graphic tool quantitative variables or different distributions can be represented something that a histogram traditionally does not do, in a quick and easy way. It also has the virtue of being visible to the naked eye.

For this reason it is widely used within the social sciences and economic sciences, thus allowing useful comparisons to be established between the different results of the same process.

Frequency polygon characteristics

frequency polygons are formed by joining the midpoints of each phase or column using straight line segments so they consist of a type of visual representation of quantitative information. The data in the table is always below the curvature of the polygon, and its highest point is always the one with the highest frequency of the set.

What is a frequency polygon used for?

Frequency polygons are used when necessary plot or highlight different joint distributions or a cross classification of a continuous quantitative variable, along with another discrete qualitative or quantitative variable, all within the same graph.

How to make a frequency polygon?

As we have already said, a frequency polygon is always obtained from a frequency histogram, when all the midpoints of each element are consequently joined with their respective frequency. To do this, the following steps must be followed:

Collect quantitative information of what will be studied. Afterwards, the lower and upper limits of all the elements studied will be established.
Determine the frequency of each type of element within the established limits, and the average calculation of the limits will be made.
Plot the line graph closed, joining the midpoints of the data obtained.

Examples of frequency polygons

frequency polygon example compare — A frequency polygon can be used to compare two variables.

frequency polygon examples — A frequency polygon can be made digitally or manually.

Frequency polygon in Excel

excel-frequency polygon — Excel allows you to graphically represent the loaded data.

To make a frequency polygon using the Microsoft Excel computer tool, we must follow the following steps:

First obtain the data table from which you want to graph a frequency polygon.
Find the “insert” menu, and choose the options “graph”, then “line” and finally “line with markers”.
A blank box will appear.
In the box, in the range of the graph, place the data from the frequency column.
In the same box, on the horizontal axis, choose the “edit” option to place the average.
Press “accept” to obtain the graph. Remember that it must be a closed graph, so we will often have to add data for the new intervals (in that case we will add the number 0 to each one).

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