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Unformatted text preview: 1 Chapter 6 Polynomials and Factors 2 1 2 Y x x e β β β = + + + is a quadratic regression. Polynomial regression function of degree d 1 d d Y x x e β β β = + + + + L Second order regression with two predictors 2 2 1 1 2 2 11 1 22 2 12 1 2 Y x x x x x x e β β β β β β = + + + + + + In practice, people seldom fit any polynomial function of degree 3 d > . End effect of polynomial regression Factors Data Weights Gender 76.5 120.5 M 1 Female n Female M 175.6 205.4 M 2 Male n Male M 1 2 n n n + = Gender is a factor. Factors can have two levels: male / female many levels: red, blue, yellow 2 dummy variable: takes value 1 for one of categories and 0 for other categories. 1 1, 0, Gender is female u otherwise = 2 1, 0, Gender is male u otherwise = Linear model 1 1 1 2 2 * * Weights u u e β β = + + Linear model 2 2 2 * Weights u e β β = + + The factor rule: A factor with d levels can be represented by at most d dummy variables. If the intercept is in the mean function, at most dummy variables....
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This note was uploaded on 12/12/2010 for the course STAT 425 taught by Professor Ma,p during the Fall '08 term at University of Illinois, Urbana Champaign.
- Fall '08