Dear all,
I'm currently a little confused with the association statistic produced by the logistic procedure in SAS 9.2. If I ask for the ROC plot and I activate ODS GRAPHICS I receive slightly different values for the association statistics (e.g., c-value, Sommer's D, etc) as if I turn off the graphics.
For illustration, please find attached an example data set (SAS/STAT UG Example 51.2) and code with and without ROC curve. If you compare the association statistics between both codes, you'll see the slight differences in the output of the association statistics. In my "real life" data set the difference is much more pronounced.
Does anyone of you know where the difference comes from? Is this difference documented, e.g. in the user's guide?
Any help is highly appreciated.
Thanks,
Thorsten
Data Neuralgia;
input Treatment $ Sex $ Age Duration Pain $ @@;
datalines;
P F 68 1 No B M 74 16 No P F 67 30 No
P M 66 26 Yes B F 67 28 No B F 77 16 No
A F 71 12 No B F 72 50 No B F 76 9 Yes
A M 71 17 Yes A F 63 27 No A F 69 18 Yes
B F 66 12 No A M 62 42 No P F 64 1 Yes
A F 64 17 No P M 74 4 No A F 72 25 No
P M 70 1 Yes B M 66 19 No B M 59 29 No
A F 64 30 No A M 70 28 No A M 69 1 No
B F 78 1 No P M 83 1 Yes B F 69 42 No
B M 75 30 Yes P M 77 29 Yes P F 79 20 Yes
A M 70 12 No A F 69 12 No B F 65 14 No
B M 70 1 No B M 67 23 No A M 76 25 Yes
P M 78 12 Yes B M 77 1 Yes B F 69 24 No
P M 66 4 Yes P F 65 29 No P M 60 26 Yes
A M 78 15 Yes B M 75 21 Yes A F 67 11 No
P F 72 27 No P F 70 13 Yes A M 75 6 Yes
B F 65 7 No P F 68 27 Yes P M 68 11 Yes
P M 67 17 Yes B M 70 22 No A M 65 15 No
P F 67 1 Yes A M 67 10 No P F 72 11 Yes
A F 74 1 No B M 80 21 Yes A F 69 3 No
;
proc logistic data=Neuralgia ;
class Treatment Sex;
model Pain= Treatment Sex Treatment*Sex Age Duration / expb;
run;
ods graphics on;
proc logistic data=Neuralgia plots(only)=(roc ) ;
class Treatment Sex;
model Pain= Treatment Sex Treatment*Sex Age Duration / expb;
run;
ods graphics off;