This document provides an introduction to different types of data displays used in statistics, including bar graphs, pie charts, histograms, and when each is most appropriate. Qualitative data that can be sorted into categories is best displayed using bar graphs or pie charts, while quantitative numerical data is best shown using histograms. Key factors in determining the best graph include whether the data is qualitative or quantitative, paired, categorical, or measured on a numerical scale. Histograms depict the distribution of numerical data by frequency across ranges or "bins".

1. INTRO TO STATISTICS
Data Displays

2. Graphs in Statistics
• Different situations call for different types of graphs.
• Many times the type of data determines what graph is
appropriate to use.
• Categories of data:
• Qualitative data, quantitative data and paired data each use
different types of graphs.

3. Qualitative data
• Qualitative data can be arranged into categories that are
not numerical.
Think “quality”
• These categories can be physical traits, gender, colors or
anything that does not have a number associated to it.
• Qualitative data is sometimes referred to as categorical
data.
Examples:
The hair colors of players on a football team
The color of cars in a parking lot
The letter grade of students in a classroom
The types of coins in a jar

4. Quantitative Data
• Quantitative data is numerical.
think “quantity” aka “how many”
• It is acquired through counting or measuring.
Examples:
heights of players on a football team
The number of cars in each row of a parking lot
The percent grade of students in a classroom
The values of homes in a neighborhood

5. Paired data
• Sometimes statistical studies want to determine the
relationship between two quantities.
An Example of Paired Data
Suppose a teacher counts the number of
homework assignments each student
turned in for a particular unit, and then
pairs this number with each student’s
percentage on the unit test. The pairs are
as follows:
(10, 95%) (5, 80%) (9, 85%) (2, 50%) (5,
60%) (3, 70%)

6. Most Common Data Displays
• Bar graph
• Pie chart
• Histogram

7. Bar Graphs
• A bar graph is a way to visually represent qualitative data.
• the information you’re looking at should be categorical,
not numerical.
• The bars are arranged in order of frequency, so that more
important categories are emphasized.

8. Which one is better?
Winter
Fall Gas Bill
Summer Electric Bill
Spring Water Bill
0 2 4 6
6
5
4
3
2 Water Bill
1 Electric Bill
0 Gas Bill

9. What’s wrong with this graph?

10. Pie Chart
• A pie chart displays qualitative data in the form of a pie.
Each slice of pie represents a different category.
Sales
4th Qtr, 1.2
3rd
Qtr, 1.4
2nd Qtr, 3.2 1st Qtr, 8.2

11. What’s wrong with this pie chart?

12. Which is better?
Both pie charts and bar graphs display qualitative data.
A pie chart or a bar graph?
Sales 4th Sales
Qtr, 1.2
10 8.2 3rd
Qtr, 1.4
5 3.2
1.4
1.2
0 2nd 1st
Qtr, 3.2 Qtr, 8.2
1st 2nd
Qtr Qtr 3rd 4th
Qtr Qtr

13. The notorious Histogram
• Histograms allow a visual interpretation of numerical data
by indicating the number of data points that lie within a
range of values, called a class or a bin.
• The frequency of the data
• that falls in each class is
depicted by the use of a bar.

15. Which is a histogram and which is a bar
graph? And WHY?

16. Histogram or bar graph?

17. Histogram or bar graph?

18. Last one

19. Differences
Bar Graph Histogram

20. Your task
1) Create a data display (graph) for each of your
questions.
a) is the data qualitative or quantitative?
b) decide which type of graph you are going to use
c) explain why you chose that graph
d) what does the data tell you/ how does it help you
in planning your event?
2) Write up two summaries of your event.
a) The before: Who, what, when, where, why
b The after: How did it go? Give a pretend summary
of events. State how many people went. How much did you
make (if a charity)?