1. Displaying and Describing Categorical Data

2. The Three Rules of Data Analysis
1) Make a picture.
2) Make a picture.
3) Make a picture.

3. Ways to display categorical data
Frequency Table – lists categories and counts for each
T-shirt size
Frequency XS S M L XL

4. Ways to display categorical data
Relative Frequency Table – lists categories and
percentages for each
T-shirt size
Relative Frequency XS S M L XL

5. Ways to display categorical data
Bar Chart – Shows a bar representing the count (frequency) or percentage (relative frequency) for each category
Relative frequency
frequency
bus
friend
parent
drove
Method of transportation

6. Bar Chart Reminders There should be spaces between the bars
Label, Label, Label
Label each category under its corresponding bar
Label counts or percentages

7. Ways to display categorical data
Pie Chart – Each category is represented as a wedge whose area corresponds to its relative frequency

8. Ways to display categorical data
Segmented bar chart – treats each bar as the whole and divides the bar into segments representing each category
Good for comparing two sets of data

9. Ways to display categorical data
Contingency table – displays counts or percentages of individuals falling into categories of two or more variables
Marginal distribution – in a contingency table, the distribution of either variable alone

10. Example: Chapter 2 page 37 #16
Winter Olympics 2010
Twenty six countries won metals in the 2010 Winter Olympics. The table lists them, along with the total number of metals each won:
Country
Metals
United States 37
Poland 6
Germany 30
Italy 5
Canada 26
Japan
Norway 23
Finland
Austria 16
Australia 3
Russia 15
Belarus
South Korea 14
Slovakia
China 11
Croatia
Sweden
Slovenia
France
Latvia 2
Switzerland 9
Great Britain 1
Netherlands 8
Estonia
Czech Republic
Kazakhstan