# Ch 9 Regression Wisdom Mrs Johnson AP Statistics.

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Ch 9 Regression Wisdom Mrs Johnson AP Statistics

What to watch out for: O Make sure the data is straight O Check the Residual Plots O Scattered above and below with no apparent pattern O No major gaps or outliers O Look for subsets in your data that might need to be looked at separately

What to watch out for: O Extrapolation O It is rarely a good idea to go beyond the limits of your data set to make predictions for values. O Stay within your data set O Data points that could be considered outliers, have strong leverage or be influential points

Outliers O Can be an outlier in the x direction or the y direction O Can be influential points –if you remove point, does slope change? O Can be points with LARGE residual or SMALL residual - distance from LSLR O Can be points that have large leverage or small leverage – think of leverage in terms of a moment arm… (i.e. x is far from x-bar)

Leverage – High/Low? Influential point – Yes/No? Residual – Large/Small? What would happen to correlation if r was removed? r would get closer to positive one AS the scatter decreases

Leverage – High/Low? Influential point – Yes/No? Residual – Large/Small? ? What would happen to correlation if r was removed? r would get closer to positive one AS the scatter decreases

Leverage – High/Low? Influential point – Yes/No? Residual – Large/Small? ? What would happen to correlation if r was removed? r would get SLIGHTLY less positive as the scatter would increase

Leverage – High/Low? Influential point – Yes/No? Residual – Large/Small? ? What would happen to correlation if r was removed? r would get closer to 1 as the scatter would decrease

Life Expectancy – Ch 9 #24 CountryBirths/W oman Life Expect CountryBirths/W oman Life Expect Argentina2.577Guatemala4.768 Bahamas2.277Honduras4.072 Barbados1.878Jamaica2.577 Belize3.574Mexico2.875 Bolivia464Nicaragua3.671 Brazil2.271Panama2.576 Canada1.582Paraguay472 Chile2.279Peru3.171 Colombia2.774Puerto Rico3.171 Costa Rica2579US2.180 Dom. Rep2.873Uruguay2.378 Ecuador3.171Venezuela2.976 El Salvador3.272Virgin Islands 2.479

Complete the following: O Create a scatterplot and describe association O Any countries that seem to not fit pattern? O Find correlation and interpret R 2 O Find LSLR O Is the line an appropriate model? O Interpret slope and y- intercept O If government leaders want to increase life expectancy, should they encourage women to have fewer children?