|Class 9 Maths Statistics||Frequency Polygon|
One more way to represent quantitative data is using its frequency. If we join the mid points of the upper sides of the adjacent rectangles off the histogram, we get frequency polygon. It is a better representation, since you can see the slope (rate of increase or decrease of value).
Also, observe that though there exists no class preceding the lowest class & no succeeding the highest class, addition of 2 class interval with frequency0 enables us to move the area of frequency polygon same as area of histogram. Area of frequency polygon is equal to area of histogram.