DRILL Put these correlations in order from strongest to weakest. {.85, -.9, .256, 0, -.1, .75, -.48} 2) In general which values show the strongest possible correlation? 3) If you get 200 females and 200 males to take a test and the average score for females is 93% and the average score for males is 48% would you be confident saying females will do better on this test than males?

Interpreting Correlation and Regression 4.2 Interpreting Correlation and Regression

Extrapolation Is when you predict a y-value using an x-value outside of the data range. (domain)

Lurking Variables Variables that may not have been measured or thought about, but may effect the data collected or given. This is why it is important to state which variables are being recorded when collecting data.

Exercise 4.20 A group of college students believes that herbal tea has remarkable powers. To test this belief, they make weekly visits to a nursing home, where they visit with the residents and serve them herbal tea. The nursing home staff reports that after several months many of the residents are more cheerful and healthy.

Correlation The correlation of a group of data appears stronger than it actually is when data is collected by recording averages of groups rather than individual data. Ex: Average energy used in a given month.

Relationships Causation: Changes in “x” cause changes in “y” Common Response: Both “x” and “y” respond to changes in some unobserved variable(s). Confounding: The effect on “y” of the explanatory variable “x” is hopelessly mixed up with the effects on “y” on other variables.

Examples Quitting smoking will reduce the risk of lung cancer. 2) A students SAT score and their acceptance rates to given colleges. 3) People at a given company are polled and asked how many years they have worked for the company and then their average salaries are recorded and compared. Causation Common Response Confounding

Causation X Y Common Response X Y Z

Confounding ? X Y Z

HOMEWORK Page 213 #’s 4.22 – 4.24 Read Summary on Page 213 – 214 Page 214 – 215 #’s 4.25, 4.27 – 4.29