Glossary term
Histogram: Meaning and Definition
Reviewed and approved by Dr. Anamika ShrivastavaPublished Last updated
A histogram is a graph of a frequency distribution of a continuous variable, drawn as adjacent rectangles with class intervals on the horizontal axis and frequencies on the vertical axis. The area of each bar is proportional to the frequency, so unequal classes need frequency density.
In more detail
In a histogram the area, not just the height, represents frequency, which is why classes of unequal width need frequency density. The bars touch because the variable is continuous. Joining the bar mid-points gives a frequency polygon, and the tallest bar locates the modal class.
Example
For 30 students with classes 0–4, 4–8, 8–12, 12–16 and 16–20 hours, the bars have heights 1, 9, 11, 8 and 1; the tallest bar marks the modal class.
Key points
- Bars touch because classes are continuous.
- Use frequency density for unequal classes.
- The tallest bar points to the mode.
Common mistake
Drawing gaps between the bars of a continuous variable.
Related terms
Where it is explained
This term is explained in Class 11 Statistics Chapter 4: Presentation of Data.