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

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

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

Two Qualitative Variables Exercise 3.39 Frequency counts

Two Qualitative Variables

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

One Quantitative Variable and One Qualitative Variable Exercise 3.40 Contact lenses

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

Two Quantitative Variables Timeplot Exercise 3.67 Old book data.

Two Quantitative Variables Scatterplot Exercise 3.68 Old book data.

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

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

Three or more Quantitative Variables Scatterplot Matrix

Next Time Review for the Quiz and Midterm