Goodness of Fit
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# Goodness of Fit ## R-squared $$ R^2 = 1 - \frac{SS_{res}}{SS_{tot}} = \frac{SS_{reg}}{SS_{tot}} $$ - Proportion of variance explained by the model - Always increases when adding predictors ## Adjusted R-squared $$ R^2_{adj} = 1 - \frac{SS_{res}/(n-p)}{SS_{tot}/(n-1)} $$ - Penalizes model complexity - Can decrease...

Goodness of Fit
R-squared
R2=1−SStotSSres=SStotSSreg- Proportion of variance explained by the model
- Always increases when adding predictors
Adjusted R-squared
Radj2=1−SStot/(n−1)SSres/(n−p)- Penalizes model complexity
- Can decrease when adding useless predictors
Partial F-Test
Test whether a subset of predictors collectively contribute: