Measures of Dispersion for Grouped Data
Histogram
A bar chart for grouped data where bar area represents frequency.
| English | Histogram |
|---|---|
| Bahasa Melayu | Histogram |
| 中文 | 直方图 |
How it is used
For classes of equal width with frequencies 3, 7, 12, 6, 2, draw bars of those heights side by side with no gaps. The tallest bar, height 12, is the modal class 21–30, and drawing crossing lines from its neighbours' tops down to the axis estimates the mode.
Where it shows up in SPM
In grouped-data statistics, Form 5, usually Paper 2. You may be asked to draw a histogram from a frequency table using class boundaries on the horizontal axis, then use it to state the modal class or estimate the mode.
Bars touch because the data is continuous.
Don't confuse it with
Open the chapter: Measures of Dispersion for Grouped Data →
Frequently asked questions
Why are there no gaps between the bars?
Because the data is continuous, one class ends exactly where the next begins at a shared boundary, such as 20.5. The bars touch to show there are no missing values between the classes, unlike a bar chart of separate categories.
How do I estimate the mode from a histogram?
On the tallest bar, draw a line from its top-left corner to the top-left corner of the bar on its right, and from its top-right corner to the top-right corner of the bar on its left. Drop down from where the two lines cross to read the mode.