Page 197 - Maths Skills - 8

Data Handling 195

HISTOGRAM
The graphical representation of grouped data is called a histogram. It consists of rectangles with class intervals
as the bases and the corresponding frequencies as heights, such that there is no gap between any two successive
rectangles.
We follow these steps for drawing histograms:
Step 1: The class intervals of the grouped data are drawn on the X-axis.
Step 2: The frequencies are plotted on the Y-axis.

Step 3: The rectangles drawn are proportional to the frequencies of their classes.

Let’s Attempt

Example 1: The following table shows the marks obtained by 50 students in an entrance examination. Draw a
histogram for this data.

Marks obtained 0 – 10 10 – 20 20 – 30 30 – 40 40 – 50

Number of Students 12 14 10 8 6

Solution: We take class intervals (marks) on the X-axis and frequencies (students) on the Y-axis.

On the Y-axis, 1 unit represents 2 students.

Fact-o-meter

Difference between a histogram and a bar graph
In a bar graph, the height of each bar matters, not
its width. It is preferably made for ungrouped data.
In a histogram the width as well as the height of
each rectangle matters because the areas of the
rectangles are proportional to the corresponding
class frequencies. Histogram is constructed for
grouped data.