Regression is the Most Used and Most Abused Technique in Statistics Assumptions: A line adequately models the data Homoscedasticity – same scatter of points along entire line Residuals at any given value of the explanatory variable are normally distributed Residuals at any given value of the explanatory variable are independent Intro Advanced Linear Regression

A Line Models the Data 120 120 100 100 80 80 80 100 120 80 100 120 120 120 100 100 80 80 80 100 120 80 100 120 Linear Regression

Homoscedasticity 120 100 80 80 100 120 120 120 100 100 80 80 80 100 120 80 100 120 Linear Regression

Other Problems Outliers Influential Points a problem because the model does not fit that point may or may not remove Influential Points a point that would markedly change the line if it were removed typically an outlier in the x direction Linear Regression