1. CHAPTER 27 PART 1 Inferences for Regression

2. YearRate 19710.08 19740.10 19750.13 19780.15 19810.18 19810.20 19850.22 19880.25 19910.29 19950.32 This table lists postal rates for first class mail, gathered by the US Postal Service.

3. We want to know if the association in our sample provides evidence that there must be an association between the two variables in the population.

4. Assumptions and Conditions for Inferences by Regression Read about these on pages 651- 653. There are a lot of them.

5. The slope of the regression line for all possible samples follows a t-model with n-2 degrees of freedom.

6. In TI-84 Calculator: STAT  TESTS  F:LinRegTTest How to get t-score and P-value

7. In TI-84 Calculator: STAT  TESTS  G:LinRegTInt How to get a Confidence Interval

8. Using the data from your worksheet (Anxiety Level and Math Test), perform a hypothesis test and create a 95% confidence interval for slope for the anxiety and math test data.

9. STAT  TEST  F:LinRegInt With a P-value of 0.0084, we reject the null hypothesis stating that there is no association between math test scores and anxiety level. There is strong evidence that, on average, lower anxiety level is associated with higher math scores.

10. STAT  TEST  G:LinRegInt We are 95% confident that the interval (-7.702, -1.271) contains the average math test score difference associated with difference in anxiety level. Each additional unit of anxiety level is associated with an average decrease of between 1.271 and 7.702 points on the math test.

11. Today’s Assignment:  Page 673 #2 and worksheet  Read about conditions & assumptions – we will use these tomorrow