May 7 - o Line doesn’t represent anything useful...

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May 7, 2008 Bivariate correlation and regression Introduction o We have two variables that are continuous: interval or ration level o One is an independent variable (X); one is a dependent variable (Y) Scatter plot 1: positive correlation / positive relationship o When one (independent) variable goes up, the other (dependent) variable goes up Scatter plot 2: negative correlation / negative relationship o When one (independent) variable goes down, the other (dependent) goes down Scatter plot 3; no correlation / no relationship
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Unformatted text preview: o Line doesn’t represent anything useful Regression line o Summarizes the scatter plot Cuts through the middle o Goes through the means of X and Y Goes through the average of X and Y o Minimizes residuals o Lets us make predictions for Y, based on X o E.g., what homicide rate would we predict in the poverty level is 20? o Out predictions are inexact, but they improve our ability to predict than if we had no information ( I have an example hand written if you would like to see it)...
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