Question

Draw a frequency polygon for the following data:

Class	15 - 20	20 - 25	25 - 30	30 - 35	35 - 40	40 - 45
Frequency	5	12	15	26	18	7

Answer 1

We take the class limits on the x-axis and the frequencies on the y-axis on suitable scales.
Now, find class marks of all the class intervals. Locate the points (x₁, y₁) on the graph, where x₁ denotes the class mark and y₁ denotes the corresponding frequency. Join all the points plotted above with straight line segments. Join the first point and the last point to the points representing class marks of the class intervals before the first class interval and after the last class interval of the given frequency distribution.

Here as the class limits do not start from 0, we put a kink between 0 and the lower boundary of the first class.