C-statistic

[d.b.pana...@usa.net]

I would like to know whether we can calculate C-statistic using SPSS
13.

[Bruce Weaver]

On Jan 16, 2:50 pm, d.b.panagiota...@usa.net wrote:
> I would like to know whether we can calculate C-statistic using SPSS
> 13.

What is the C-statistic? Please provide more information.

--
Bruce Weaver
bwe...@lakeheadu.ca
www.angelfire.com/wv/bwhomedir
"When all else fails, RTFM."

[Bruce Weaver]

On Jan 16, 2:54 pm, Bruce Weaver <bwea...@lakeheadu.ca> wrote:
> On Jan 16, 2:50 pm, d.b.panagiota...@usa.net wrote:
>
> > I would like to know whether we can calculate C-statistic using SPSS
> > 13.
>
> What is the C-statistic? Please provide more information.
>

Oops...I forgot to add that questions about how to do something in
SPSS are more appropriate in the SPSS newsgroup. I've cross-posted
this reply there.

[Ryan]

On Jan 16, 2:50 pm, d.b.panagiota...@usa.net wrote:

> I would like to know whether we can calculate C-statistic using SPSS
> 13.

If by the "c-statisitc" you are referring to the measure of the
discriminative power of the logistic equation, you can calculate it by
saving the predictive probabilities from the logistic regression
analysis and running a ROC curve with the preditive probabilities as
the "test variable." The c-statistic is the area under the curve
value. HTH

[Frank E Harrell Jr]

In R/S-Plus you can just use the lrm function in the Design package or:

mean.rank <- mean(rank(x)[y == 1])
c.index <- (mean.rank - (n1 + 1)/2)/(n - n1)

(where n1 is the number of observations with y=1)

or use the somers2 function in the Hmisc package.

Frank Harrell