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3.3: Correlation and Regression Wisdom

3.3: Correlation and Regression Wisdom. Outlier vs. Influential point. Child 19 = outlier (but doesn’t affect regression line much due to other points with similar x-values nearby)

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3.3: Correlation and Regression Wisdom

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  1. 3.3: Correlation and Regression Wisdom

  2. Outlier vs. Influential point • Child 19 = outlier (but doesn’t affect regression line much due to other points with similar x-values nearby) • Child 18 = influential point, small residual (close to line but far out in x-direction, strong influence on regression line)

  3. Misc. • Not all outliers are influential • The LSRL is most likely to be heavily influenced by observations that are outliers in the x direction. • Influential points often have small residuals since they pull the LSRL towards themselves. • Find the LSRL with and without the suspect point. If the line moves more than a small amount, the point is influential.

  4. Strong positive linear association. The correlation is r = .9749. Since r-sq = .9504, the regression of of y on x will explain 95% of the variation in the values of y. No economic relationship between these two! Lurking variable: common year. Both imports and health spending grew rapidly in these years.

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