Graphical Representation of Data
A Bar graph is a graphical representation of the numerical data by a number of bars (rectangles) of uniform with erected horizontally or vertically with equal spacing between them.
Graphical representation of numericals data in the form of bars with fixed (equal) width and varying height.
Method to draw Bar Graphs :
Step 1 : Draw a horizontal line OX also called as x-axis and a vertical line OY also called as y-axis.
Step 2 : Mark points at equal intervals along x-axis. Write the names of the data whose values are to be plotted.
Step 3 : After choosing a suitable scale, determine the heights of the values of the respective data names.
Step 4: Mark off these heights parallel to the y-axis from the points taken in step 2.
Step 5 : On the x-axis draw bars of equal width for the heights marked in step 4. The bars should be centered on the points marked on the x-axis. These bars represent the given numerical data.

Illustration 13
In a particular section of Class VIII, 40 students were asked about the months of their birth and the following graph was prepared for the data so obtained :

(i)     How many students were born in the month of November ?
(ii)     In which month were the maximum number of students born ?
(iii)     In which month were the minimum number of students born ?
Solution
Note that the variable here is the ‘month of birth’, and the value of the variable is the ‘Number of students born’.
(i)     2 students were born in the month of November.
(ii)     The maximum number of students were born in the month of September.
(iii)     The minimum number of students were born in the month of June.