1. GRAPHS
PREPARED BY: ENAWOID

2. 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.

3. 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).

4. 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).

5. 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

6. 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?

7. 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.

8. 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)

9. 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.

10. 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.

11. 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.

12. 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.

13. 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

14. 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

15. 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

16.  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