Frequency Polygon Calculator
Create a frequency polygon table from raw data by grouping into equal-width classes and computing midpoints.
Data points: 12
Classes used: 4
| Class Interval | Midpoint | Frequency | Relative Frequency |
|---|---|---|---|
| [12.00, 17.00) | 14.50 | 4 | 0.333 |
| [17.00, 22.00) | 19.50 | 2 | 0.167 |
| [22.00, 27.00) | 24.50 | 4 | 0.333 |
| [27.00, 32.00] | 29.50 | 2 | 0.167 |
How to Use This Calculator
- Enter raw data values for the variable of interest.
- Select the number of classes or accept the default √n guideline.
- Plot midpoints against frequencies to draw the frequency polygon by connecting points.
- Optionally include tails at zero frequency to close the polygon when charting.
Formula
Frequency polygons use the same grouped data as histograms. The midpoint of each class interval is plotted against the class frequency and points are connected with straight lines.
Frequently Asked Questions
Why use a frequency polygon instead of a histogram?
Polygons make it easier to compare multiple distributions on the same axes and highlight trends across classes.
How do I close the polygon?
Add points at the start and end with zero frequency to ensure the lines descend to the baseline.
Can I use unequal class widths?
Polygons work best with equal-width classes. Unequal widths distort the relationship between class width and frequency.