Page 1 - Lesson note-4- Ch 14 Statistics( Frequency Polygon)

SAI International Residential School
Class –IX

Mathematics

Chapter-14: Statistics

LESSON NOTE-4

Sub topics: Frequency Polygon.

Frequency Polygon

A frequency polygon is almost identical to a histogram, which is used to compare sets of
data or to display a cumulative frequency distribution. It uses a line graph to represent
quantitative data.

Steps to draw Frequency Polygon

To draw frequency polygons, first we need to draw histogram and then follow the below
steps:

• Step 1- Choose the class interval and mark the values on the horizontal axes
• Step 2- Mark the mid value of each interval on the horizontal axes.
• Step 3- Mark the frequency of the class on the vertical axes.
• Step 4- Corresponding to the frequency of each class interval, mark a point at
the height in the middle (mid-point) of the class interval.
• Step 5- Connect these points using the line segment.
• Step 6- The obtained representation is a frequency polygon.

EXAMPLES
Example-1:

In a batch of 400 students, the height of students is given in the following table.
Represent it through a frequency polygon.

Solution: Following steps are to be followed to construct a histogram from the given
data: