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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 1unit 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.
 Fall '11
 WilliamThomas

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