QUANTITATIVE REASONING I
Interpreting and Estimating Bar Graphs
INTRODUCTION:
 A Graphical representation is a visual
display of data and statistical results.
 It is more often and effective than
presenting data in tabular form.
 There are different types of graphical
representation and which is used depends on
the nature of the data and the nature of the
statistical results.
CONTI…
 Graphical representation is the visual display of
data using plots and charts.
 Graphical representation helps to quantify, sort
and present data in a method that is
understandable to a large variety of audience.
 Several types of mediums are used for expressing
graphics, including plots, charts and diagrams.
BAR GRAPH
 It is a graph that consists of bars for each
category with the length/height of the bars
specifying the frequency for each category.
 One axis will indicate the categories and the
other axis will indicate the frequency.
 Bar graphs are often used for comparing different
characteristics of items. Bar graphs can have
horizontal or vertical bars.
CONTI…
 A bar graph (also known as a bar chart) is a
visual representation of data where rectangular
bars (either vertical or horizontal) represent the
values of different categories.
 Bar graphs are used to compare different
categories and see the differences in their values
easily.
A BAR DIAGRAM:
 A graph showing the differences in frequencies or
percentages among the categories of a nominal or an
ordinal variable.
 A Bar graph is a chart with rectangular bars with length
proportional to the values that they represent.
BAR GRAPH
Xaxis
• Represents categories
or groups.
Yaxis
• Represents the
quantity or
measurement
associated with the
categories.
KEY FEATURES:
Bar: The length or height of the
bar corresponds to the value.
Labels: Identify the categories
(x-axis) and values (y-axis).
Gridlines :Help in estimating
the values of bars.
Title :overall theme or subject of
the graph
STEPS TO INTERPRET A BAR GRAPH
Examine
the Title
Estime
data
Analyze
the Axes
Look for
trends
and
patterns
Identify
the Bars
Compare
the bars
CLASS SURVEY FOR FAVORITE SPORT
QUESTIONS
 How many students said basketball was their
favorite?
 How many more students liked Football than
Soccer?
ESTIMATING DATA FROM BAR GRAPHS
Estimating
the values
• To estimate the value of a bar, use the
gridlines on the y-axis. For example, if
the bar is between 30 and 40 units, you
can estimate its value as 35.
Estimating
differences
• To estimate the difference between two
bars, subtract the value of one bar
from the other
Estimating
averages
• If you want to find the average of
values represented by bars, add the
values of all the bars and divide by the
number of bars.
1.SIMPLE BAR DIAGRAM:
 It represent only one variable.
for example sales, production, population figures
etc..
 These are in same width and vary only in
heights.
 It becomes very easy for readers to study the
relationship. It is the most popular in practice.

2.SUB DIVIDED OR COMPONENT BAR
DIAGRAM:
 While constructing such a diagram the
various components in each bar should be
kept in the same order.
 The components are shown with
different shades or colours with a
proper index.
3.MULTIPLE BAR DIAGRAM:
 This method can be used for data which
is made up of two or more components.
 In this method the components are
shown as separate adjoining bars.
 The components are shown by different
shades and colours.