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GRAPHS
PREPARED BY: MANOJ PATEL
ASST. PROFESSOR
JHUNJHUNWALA BUSINESS SCHOOL
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AIMS:
Interpret and analyze graphs to determine what
information is given.
Complete exercises by applying data and graph concepts.
Self-assess knowledge and skills acquired from this unit.
Develop problem-solving skills.
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DEFINITION:
A graph is a visual representation of a relationship between,
but not restricted to, two variables. A graph generally takes
the form of a one- or two-dimensional figure such as a
scatterplot. Although, there are three-dimensional graphs
available, they are usually considered too complex to
understand easily.
A graph commonly consists of two axes called the x-axis
(horizontal) and y-axis (vertical). Each axis corresponds to
one variable. The axes are labelled with different names, such
as Price and Quantity.
The place where the two axes intersect is called the origin.
The origin is also identified as the point (0,0).
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A GOOD GRAPH
accurately shows the facts
grabs the reader's attention
complements or demonstrates arguments presented in
the text
has a title and labels
is simple and uncluttered
shows data without altering the message of the data
clearly shows any trends or differences in the data
is visually accurate (i.e., if one chart value is 15 and
another 30, then 30 should appear to be twice the size of
15).
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WHY USE GRAPHS WHEN PRESENTING DATA?
are quick and direct
highlight the most important facts
facilitate understanding of the data
can convince readers
can be easily remembered
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GRAPHS: FOUR GUIDELINES
1. Define your target audience.
Ask yourself the following questions to help you
understand more about your audience and what
their needs are:
Who is your target audience?
What do they know about the issue?
What do they expect to see?
What do they want to know?
What will they do with the information?
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2. Determine the message(s) to be transmitted.
Ask yourself the following questions to figure out what
your message is and why it is important:
What do the data show?
Is there more than one main message?
What aspect of the message(s) should be highlighted?
3. Determine the nature of the message.
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4. Experiment with different types of graphs and select
the most appropriate.
pie chart (description of components)
horizontal bar graph (comparison of items and
relationships, time series)
vertical bar graph (comparison of items and
relationships, time series, frequency distribution)
line graph (time series and frequency distribution)
scatter plot (analysis of relationships)
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TYPES OF GRAPHS
1. bar graph may be either horizontal or vertical. The
important point to note about bar graphs is their bar
length or height—the greater their length or height,
the greater their value.
Bar graphs are one of the many techniques used to
present data in a visual form so that the reader may
readily recognize patterns or trends.
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3. Pictograph - uses picture symbols to
convey the meaning of statistical
information. Pictographs should be used
carefully because the graphs may, either
accidentally or deliberately, misrepresent
the data. This is why a graph should be
visually accurate.
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4. Pie chart is a way of summarizing a set of categorical data
or displaying the different values of a given variable (e.g.,
percentage distribution). This type of chart is a circle
divided into a series of segments. Each segment represents
a particular category. The area of each segment is the same
proportion of a circle as the category is of the total data set.
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5. Line graph is a visual comparison of how two variables—
shown on the x- and y-axes—are related or vary with
each other. It shows related information by drawing a
continuous line between all the points on a grid.
Line graphs are more popular than all other
graphs combined because their
visual characteristics reveal data trends
clearly and these graphs are easy to create.
Line graphs, especially useful in the fields of
statistics and science, are one of the most
common tools used to present data.
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Pictograph uses an icon to represent a quantity of data
values in order to decrease the size of the graph. A key
must be used to explain the icon.
Advantages
Easy to read
Visually appealing
Handles large data sets easily using keyed icons
Disadvantages
Hard to quantify partial icons
Icons must be of consistent size
Best for only 2-6 categories
Very simplistic
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Pie chart displays data as a percentage of the whole. Each pie
section should have a label and percentage. A total data
number should be included.
Advantages
Visually appealing
Shows percent of total for each category
Disadvantages
No exact numerical data
Hard to compare 2 data sets
"Other" category can be a problem
Total unknown unless specified
Best for 3 to 7 categories
Use only with discrete data
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Bar graph displays discrete data in separate columns. A double bar graph
can be used to compare two data sets. Categories are considered
unordered and can be rearranged alphabetically, by size, etc.
Advantages
Visually strong
Can easily compare two or three data sets
Disadvantages
Graph categories can be reordered to emphasize certain effects
Use only with discrete data
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Line graph
A line graph plots continuous data as points and then
joins them with a line. Multiple data sets can be graphed
together, but a key must be used.
Advantages
Can compare multiple continuous data sets easily
Interim data can be inferred from graph line
Disadvantages
Use only with continuous data
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