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Construction of a Histogram

To draw a histogram, we use the following steps:

• Draw two perpendicular axes, the horizontal axis (x-axis) and the vertical axis (y-axis),
intersecting at a point (say O).

• Take a suitable scale and mark the class intervals along the horizontal axis.

• Take a suitable scale and mark the corresponding frequencies along the vertical axis.

• Construct rectangles with class intervals as bases and the respective frequencies as heights.
Let us understand it with an example. Consider the following grouped distribution table.

Age (in Years) 10-20 20-30 30-40 40-50 50-60
Number of literate males 300 600 800 500 450

1. Draw two perpendicular axes and label: age on the x-axis and number of literate males on the
y-axis.

2. Choose an appropriate scale for representing a class interval. On the x-axis, 1 unit = 10 years.
Then, mark class intervals 10-20, 20-30, 30-40, 40-50, and 50-60 along the x-axis adjacent to
each other leaving no gaps in between.

3. Choose an appropriate scale for representing frequencies. On the y-axis, 1 unit = 200 males.
Draw the bars on each class interval according to the frequency.

4. Give a title to the histogram drawn.

Thus, the histogram for the data given above will be as shown below.

Example 4: The heights of 40 students of a class are given in the following table.

Height (in cm) 120-125 125-130 130-135 135-140 140-145 145-150 150-155

Number of students 2 4 8 4 12 8 2

Draw a histogram to represent the above data.

101 Data Handling