I have two databases of patients and medications. Each database has the same patients. Both have millions of records.
My job is to select a sample from each and confirm that the medications match. So medication is a nominal variable with a huge number of levels. Any advice on selecting a sample size for this and also statistics to use beyond percent matched/unmatched. Cohen's Kappa?
Does the number of levels of the nominal variable variable effect Kappa? Would conceiving of each medication as binary make it easier?