They do not affect the baseline hazard 7 proportional

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Unformatted text preview: o not affect the baseline hazard. 7 Proportional Hazards Regression Model Model the hazard ratios (relative risks) on the log scale as function of predictors: ￿ ￿ log hazard ratio r j = β1Group + β2 X + β3 Z + . . . No intercept—it is part of baseline hazard. What makes proportional hazards regression work is that we can fit the model without needing to estimate the baseline hazard h 0(t ). Proportional hazards regression is about the hazard ratio or relative risk, not the hazard. 8 Interpretation of the regression coefficients is very similar to logistic regression: • Class variable A : ˆ exp(βi ) is the hazard ratio or relative risk comparing i -th level of A to reference level. • Continuous variable X : ˆ exp(β j ) is relative risk corresponding to a 1-unit increase in X , comparing those with X = x + 1 to those with X = x . 9 Breast cancer example Study in 1987 compared survival times of women diagnosed with breast cancer divided into two groups: staining test of biopsy tissue pos...
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This note was uploaded on 11/21/2011 for the course PUBH 6470 taught by Professor Williamthomas during the Fall '11 term at University of Florida.

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