Frequency polygon
Topic: Geographical Data: Sources, Compilation and Processing · NCERT: Class 12, Ch 1 "Data - Its Source and Compilation"
Meaning
A frequency polygon is a line graph of a frequency distribution. Each class frequency is plotted as a point, usually above the class midpoint (the middle value of the class), and the points are joined by straight lines. It shows the shape of the distribution clearly. Because the lines do not hide each other, two or more distributions can be drawn on the same chart and compared easily.
Example
NCERT uses a frequency polygon (Fig. 1.5) to show the spread of students' scores across score classes. If the scores of two classes of students were drawn on one graph, the two lines would show at once which group scored higher.
Don't confuse with
- Ogive: plots cumulative frequencies (running totals), not the frequency of each class, so its curve only rises or only falls.
Related concepts
- Grouping of data
- Class interval
- Tally marks
- Frequency distribution
- Cumulative frequency
- Exclusive method
- Inclusive method
- Ogive