[R] upperbound of C index Conf.int. greater than 1

[DAVID ARTETA GARCIA]

Dear Frank

Frank E Harrell Jr <f.harrell at vanderbilt.edu> wrote:

>
> A few observations.
>
> 1. With minimal overfitting, rcorr.cens(predict(fit), Y) gives a good
> standard error for Dxy = 2*(C-.5) and bootstrapping isn't very necessary
>
> 2. If you bootstrap use the nonparametric bootstrap percentile method
> or  other methods that constrain the confidence interval to be in [0,1].
>
> 3. I don't know why the model would be linear on the two predictors you
> are using.

Do you mean using these predictors fitted with spline functions?? I  
have read about it in your "Regression Modeling Strategies" but I am  
not very sure I understand the use of them. I will read through it  
again.

David

>
> Frank
>
> -- 
> Frank E Harrell Jr   Professor and Chair           School of Medicine
>                      Department of Biostatistics   Vanderbilt University