Estimate diagnostic accuracy (sensitivity, specificity, etc) and agreement statistics when one test is conducted on only a subsample of specimens A standard test is observed on all specimens. We treat the second test (or sampled test) as being conducted on only a stratified sample of specimens. We treat the total sample as stratified two-phase sampling and use inverse probability weighting. We estimate diagnostic accuracy (category-specific classification probabilities; for binary tests reduces to specificity and sensitivity) and agreement statistics (percent agreement, percent agreement by category, Kappa (unweighted), and symmetry tests (reduces to McNemar's test for binary tests)). Software Hormuzd Katki <katkih@mail.nih.gov> Hormuzd A. Katki and David W. Edelstein GPL-3 2011-04-04 application/tgz http://CRAN.R-project.org/package=CompareTests