[R] difference between coxph and cph

[Deb Montgomery]

Hi. I am using Windows version of R 1.8.1. Being somewhat new to survival
analysis, I am trying to compare cph (Design) with coxph (survival) for use
with a survival data set.

I was wondering why cph and coxph provide me with different confidence
intervals
for the hazard ratios for one of the variables. I was wondering if I am
doing something wrong? Or if the two functions are calculating hazard ratios
and the 95% confidence intervals differently? I have listed part of the code
and part of the results from the 2 functions. Sorry if this question is a
repeat, I didn't find it when I searched the archives.

###########################################################
# s= Surv(Time1, Time2, censor)
#f= coxph(s~  Siblings + Weight.at.age.4)
#summary(f)
#Call:
#coxph(formula = s ~ Siblings + Weight.at.age.4)
# n= 132
#                exp(coef) exp(-coef) lower .95 upper .95
#Siblings            1.52      0.657     0.815      2.84
#Weight.at.age.4      0.91      1.099     0.772      1.07
##############################################################
#s= Surv(Time1, Time2, censor)
#f= cph(s~  Siblings + Weight.at.age.4,surv=TRUE ,  x=T, y = T)
# summary(f)
#             Effects              Response : s
# Factor          Low   High   Diff.  Effect S.E. Lower 0.95 Upper 0.95
# Siblings       0.000  1.000 1.0000  0.42  0.32 -0.20      1.04
#  Hazard Ratio   0.000  1.000 1.0000  1.52    NA  0.82      2.84
# Weight.at.age.4 8.613 10.602 1.9885 -0.19  0.17 -0.51      0.14
# Hazard Ratio   8.613 10.602 1.9885  0.83    NA  0.60      1.15


Sincerely

Deb Montgomery

Department of Fisheries and Wildlife Resources
University of Idaho
Moscow, Idaho 83843
208-885-4008
mont4260 at uidaho.edu