1. Prof. Eric A. Suess Chapter 3
Statistics 3502/6304
Prof. Eric A. Suess
Chapter 3

2. Data Description – Two or more Variables
How to plot data collected on two or more variables.
See the comparisons.
See the associations.

3. Two Qualitative Variables
Contingency Tables, 2-by-2 tables
Stacked Bar Graphs
Cluster Bar Graphs

4. Two Qualitative Variables
Exercise 3.39
Frequency counts

5. Two Qualitative Variables

6. Two tutorial website
Libre Office is an open source Office package. It has a nice spreadsheet program. Lets see an example of Categorical data and making Pivot Tables.
LibreOffice Calc Tutorials  pivot.ods
MS Excel Tutorials GCF LearnFree.org

7. One Quantitative Variable and One Qualitative Variable
Exercise 3.40
Contact lenses

8. Two Quantitative Variables
When we have two quantitative variables X and Y then we can look at the association between the variables.
Scatterplots Figure 3.31
Correlation
𝑟= 1 𝑛−1 𝑖=1 𝑛 𝑥 𝑖 − 𝑥 𝑠 𝑥 𝑦 𝑖 − 𝑦 𝑠 𝑦

9. Two Quantitative Variables
Timeplot
Exercise 3.67
Old book data.

10. Two Quantitative Variables
Scatterplot
Exercise 3.68
Old book data.

11. Correlation
The correlation coefficient 𝑟 measure the strength and direction of a linear relationship between two quantitative variables.
Correlation can been seen in scatterplots
Correlations between 3 or more variables can be seen in scatterplot marticies

12. Correlation
Exercise 3.68
Compute the correlation between Calories and Pounds of Sugar
Correlation: Pounds, Calories
Pearson correlation of Pounds and Calories = 0.986

13. Three or more Quantitative Variables
Scatterplot Matrix

14. Next Time
Review for the Quiz and Midterm