Frequency Polygon
A frequency polygon is a method to visually represent quantitative data. It is created by joining the midpoints of the upper sides of adjacent bars in a histogram with line segments. This representation offers an alternative way to visualize frequency distributions, making it easier to understand and compare different data sets.
To construct a frequency polygon:
1. Draw a Histogram: Begin by drawing a histogram to present your data visually. The histogram will show the frequencies of each class interval.
2. Find Class Midpoints: Calculate the midpoints (also called class marks) of each class interval. The class marks are determined by the formula:
Class-mark = (Upper limit + Lower limit) / 2
3. Plot the Points: Plot the class marks on the horizontal axis and their corresponding frequencies on the vertical axis.
4. Connect the Points: Join these points with straight lines to form the frequency polygon.
5. Include Zero Frequency Classes: To complete the polygon, it's important to include additional points for classes with zero frequencies at either end of the data set, ensuring the polygon accurately mirrors the histogram's area.
This method proves beneficial for comparing two sets of data, analyzing trends, and recognizing variations in frequency distribution. It also provides a clearer visual understanding than histograms alone, allowing for quicker insights into data patterns.