1. 2.2 Bar Graphs, Circle
Graphs, and Time-Series
Graphs
CHAPTER 2
ORGANIZING DATA

2. Page 55
Bar Graphs
 A bar graph can be used to display quantitative or
qualitative data.
 A clustered bar graph has two (or more) bars for
each class
 Features of a Bar Graph
 Bars can be vertical or horizontal
 Bars have the same width and there is the same amount of space
between bars
 The lengths of the bars represent values of the variable being
displayed, the frequency of occurrence, or the percentage of
occurrence. Use the same scale for each bar!
 The graph has a title, labels for each bar, and vertical scale or
actual value for the length of each bar

3. Page 55
Example 4 – Bar Graph
Figure 2-11 shows two bar graphs depicting the life expectancies
for men and women born in the designated year. Let’s analyze
the features of these graphs.  The graphs are clustered bar
graphs
 One bar represents the life
expectancy for men, and the
other represents the life
expectancy for women.
 The height of each bar represents
the life expectancy (in years).
 Figure 2-11(b) is that of a
changing scale. The scale between
0 and 65 is compressed.
 The changing scale
amplifies the apparent
Life Expectancy difference between life
spans for men and
Figure 2-11 women, as well as the
increase in life spans from
those born in 1980 to the
projected span of those
born in 2010.

4. Page 56
Pareto Charts
 A Pareto Chart is a bar graph in which that bar
height represents frequency of an event and the bars
are ordered from highest to lowest.
Example of a Pareto Chart:

5. Page 57
Circle Graphs
 A circle graph or pie chart is another way to
represent data. Wedges of the circle display
proportional parts of the total population that share
a common characteristic.
 Wedges are usually labeled with percentages
 The total quantity is 100%, represented by the entire circle
Example of a Circle Graph:

6. To Make a Circle Graph
1. Find the percentage (relative frequency or
fractional part times 100) for each class/category.
Do your percents add up to 100%?
2. Find the number of degrees for each
class/category: Number of Degrees = % • 360˚
3. Draw the circle graph. Divide the circle into wedges
with the designated number of degrees. Label each
piece with its class/category and percentage. Colors
are extremely helpful!

7. Page 58
Time-Series Graphs and Data
 A time-series graph is a graph that shows data
measurements in chronological order.
 Data are plotted in order of occurrence at regular intervals
over a period of time.
Example of a Time-
Series Graph:

8. Time-Series Graphs and Data
 Time-series data consist of measurements of the
same variable for the same subject taken at regular
intervals over a period of time.

9. To Make a Time-Series Graph
1. Put time on the horizontal scale and the variable
being measured on the vertical scale
2. Plot the data as points, connect the points with line
segments

10. Page 59
How to Decide Which Type of Graph to Use
 Bar Graphs
 Quantitative or qualitative data
 Quantitative Data: measurement itself can be shown
 Beware of changing scales and jumps
 Pareto Charts
 Identify the frequency of events or categories in decreasing order
 Circle Graphs
 Display how the total is dispersed in several categories
 Best if there are 10 or fewer wedges
 Good for qualitative data (or any data for which percentages make
sense)
 Time-series Graphs
 Display how data change over time
 Units of time should be consistent

11. For All Graphs
 Provide a title, label the axes, and identify the units
of measure.
 Do not let artwork or skewed perspective cloud the
clarity of the information displayed.
AP Test: You will
be harshly penalized
for a lack of titles and
labels!

12. Homework
 Page 60
 #1 – 6
 #8, 9, 11, 13