Hi,

I am running roctab to find the ROC area. We have repeated measures - some subjects have two observations; some subjects have one observation. I am using bootstrap to adjust for the repeated measures. I would like to sample with replacement such that either all or none of a given subject's data are included in the bootstrap sample. This is the code I have been using:

PHP Code:
bootstrap r(area), reps(1000) cluster(studyid) : roctab mems_ge90_30d inh_result_avg
estat bootstrap, all 
After running the bootstrap command, I get the following message:

PHP Code:
Warning:  Because roctab is not an estimation command or does not set e(sample),
          bootstrap has no way to determine which observations are used in calculating
          the statistics and so assumes that all observations are used.  This means
          that no observations will be excluded from the resampling because of missing
          values or other reasons.

          If the assumption is not true, press Break, save the data, and drop the
          observations that are to be excluded.  Be sure that the dataset in memory
          contains only the relevant data. 
What does that mean? We don't have any missing data for these variables. But, it also seems that it means the resampling is independent of the cluster variable (is that true - does that count as "other reasons"?). Is there a way to resample such that the observations include either all/none of a subject's data?

Thanks,
Robin