Displaying and Describing Categorical Data

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

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

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

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

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

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

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

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

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