1. 3.1Displays of Categorical Data

3. Frequency Distribution A graph or frequency table describes a distribution. A distribution tells us the possible values a variable takes as well as the occurrence of those values (frequency or relative frequency). It’s basically a list of all the things that COULD happen, and also the LIKELIHOOD that each will actually happen. Ex: Rain: 5%, No Rain: 95%

4. Pie Chart: A circle having a “slice of pie” for each category. Useful when the data adds up to a whole (100%), like an annual budget. Be careful when answering questions. Watch for key words like AND, OR, and NOT.

5. Movie Preferences… a.What percent of students like either romance or drama? b.What percent of students do not like foreign films? c.What percent of students do not like action or science fiction?

6. Bar Graph A graph that displays a bar for each category.  Easier to compare categories with a bar graph rather than with a pie chart.  The bars can be ordered several ways:  Logically: customizes the information for the reader’s ease  Alphabetically: makes it easy to locate a specific piece of information  Pareto Charts: when the categories are ordered by their frequency, from the tallest bar to the shortest bar. Useful when the focus is the few most frequent categories

7. Necessary details of a bar graph Title, which should inform the reader of the content of the graph X-axis label, usually in words, since we are using categorical data Y-axis label, with units The bars, drawn to scale. The bars should be equal in width, and have some space between them. Usually some color to make it easier to read

8. Happy Birthday! This graph has LOGICAL ordering on the x- axis, keeping the months in order. What is the mode for birthday month? What is the difference between the month with the most birthdays and the month with the least birthdays? How many students were in this survey? What percent of students have their birthdays in the summer? (June, July, August)

9. Alphabetical Bar Graph Example What are the advantages of this format? What are the drawbacks? Which grain has the most protein per ¼ cup?

10. Carbon Dioxide Emissions Worldwide Why is this data presented in a Pareto Chart form? What are the advantages of such a format?