| 5.3.1 |
Bar graphs |
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Bar graphs or bar charts are used
to display qualitative data. To construct a bar chart, we mark the
various categories on the horizontal axis. All categories are represented
by intervals of the same width. We mark the frequencies on the vertical
axis, then draw one bar for each category such that the height of the bar
represents the frequency of the corresponding category. We leave
a small gap between adjacent bars. |
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Example 5.3-1
Represent the frequency distribution
of Table 5.3 using a bar graph.
i.e. Bus. = 6, Comp. = 8, Eng. =
8, Math. = 4, Others = 12 |
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| 5.3.2 |
Pie charts |
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A pie chart is more commonly used
to display data in percentage form. The whole pie or circle represents
the total sample or population. The pie is divided into different
portions that represent the percentages of the population or sample belonging
to different categories. |
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Example 5.3-2
Represent the percentage distribution
of Table 5.3 using a pie chart.
i.e. Bus.=17%, Comp=22%, Eng.=17%,
Math.=11%, Others=33%. |
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| 5.3.3 |
Histograms |
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A histogram is a graph in which
classes are marked on the horizontal axis and either the frequencies, relative
frequencies or percentages are marked on the vertical axis. The frequencies,
relative frequencies or percentages are represented by the heights of the
bars. In a histogram, the bars are drawn adjacent to each other and without
leaving any gap between them. |
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Example 5.3-3
Use a histogram to represent the
frequency distribution of Table 5.4.
i.e. 41 - 50 = 5, 51 - 60 = 8, 61
- 70 = 8, 71 - 80 = 4. |
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| 5.3.4 |
Polygons |
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A polygon is a graph that can be
used to represent quantitative data. To draw a frequency polygon,
we first mark a dot above the midpoint of each class at a height equal
to the frequency of that class. Next, we mark two more classes, one
at each end of the existing classes, with zero frequencies and mark their
midpoints. In the last step, we join the adjacent dots with straight
lines. |
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Example 5.3-4
Use a polygon to represent the frequency
distribution of Table 5.4.
i.e. 41 - 50 = 5, 51 - 60 = 8, 61
- 70 = 8, 71 - 80 = 4. |
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