Page 140 - DLIS401_METHODOLOGY_OF_RESEARCH_AND_STATISTICAL_TECHNIQUES

Unit 9: Presentation of Data

If we observe Figures 9.1 and 9.2, we find that figure 9.2 is simpler than Fig. 9.1. Figure 9.1 Notes
is complex because the number of class intervals is more. If we further increase the number
of class intervals, the figure obtained will be still more complex. So for plotting the histogram
for a given data, usually we prefer to have less number of class intervals.

9.3.2 Bar Diagram or Bar Graph

If the variable is discrete, then a histogram cannot be constructed as the classes are not comparable
in terms of magnitude. However, a simple graphical presentation, quite similar to histogram,
known as bar graph, may be constructed. In a particular town, total number of schools is 24
and the management-wise distribution of schools is as shown earlier in Table 9.2.
Management No. of Schools

Govenment 4
Local Body 8
Private Aided 10
Private Unaided 2

Total 24
The bar graph will be as shown in Figure 9.3.

Figure: 9.3. Management-wise distribution of Schools in a Town
Y

18
16
14
Frequencies 12 8 10
10
8
6
4
4
2
2
0 Govt. Local Body Private Private X
Schools Schools Aided Unaided
Schools Schools
For a discrete variable the unit of measure on the horizontal axis is not important. Neither are
the classes related to each other. So the bars are equally spaced and are of equal width on the
horizontal axis. However, the height of the bars are proportionate to the respective frequencies.
Bar graphs are frequently used for pictorial presentation of discrete data. If two variables are
used simultaneously, even then bar graphs may be quite effective. For example, if alongwith
the total number of schools (management-wise) the number of boys’ schools, girls’ schools and
co-education schools are also to be indicated then this can be done on the same graph paper
by using different colours, each indicating the sex-wise category. For each management there
will be 4 bars having different colours indicating different categories.

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