Histogram
Topic: Graphical Representation of Data and Thematic Maps · NCERT: Class 12, Ch 3 "Graphical Representation of Data"; Class 12, Ch 4 "Spatial Information Technology"
Meaning
A histogram is a graph of a frequency distribution, which means a count of how many cases fall into each range of values (each class interval). It is drawn as bars that touch each other, with no gaps. Each bar's width is the class interval. Its height shows the frequency (strictly, the bar's area shows it). Because the bars touch, a histogram shows continuous data, where one class runs straight into the next. If you join the midpoints of the bar tops, you get a frequency polygon.
Example
Take the literacy rates of Indian states in Census 2001. They can be grouped into classes such as 47–56%, 56–65%, 65–74%, 74–83% and 83–92%. A histogram of how many states fall in each class shows touching bars, with Kerala and Mizoram in the top class.
Don't confuse with
- Bar diagram: a bar diagram has gaps between bars and shows separate categories, such as months or states. A histogram's bars touch and show continuous ranges of values.