2/22/2013

Chapter 10 - Exploring Relationships Between Numerical Variables

• Exercises 1 and 2 on p. 379 - Open Detroit Lions 2008.mtw

Common Types of Relationships

• No Association
• Positive Association
• Negative Association

Measuring the strength of assocation

• Pearson’s correlation coefficient

Properties of r

• r > 0 indicates positive association.
• r < 0 indicates negative association.
• Extreme values r = 1 and r = -1 indicate perfect linear association.
• The value of r remains unchanged if the unit of measurement of X, Y, or both changes.
• r measures only the strength of linear association between two variables.

Class Activity

• Guessing Correlations
• Another Applet for Guessing Correlations

Class Exercises for Monday

• 10.11, 10.12, 10.31, and 10.41

Please read Chapter 10 for class on Monday. We will have a problem session on Monday.