5/23/07. psa_dre_v2.dta corrects an error in psa_dre.dta - the omission of three records for white subjects with neg DRE and neg PSA
Data reference: Smith DS, Bullock AD, Catalona WJ. Racial differences in operating characteristics of prostate cancer screening tests. The Journal of Urology 158:1861-66. 1997.
patients negative for both PSA and DRE were not biopsied, thus d is missing