Biostatistics Advance Access published online on October 8, 2007
Biostatistics, doi:10.1093/biostatistics/kxm036
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A modified sign test for comparing paired ROC curves
Department of Biostatistics, University of Michigan, Ann Arbor, MI 48109, USA tombraun{at}umich.edu
Department of Preventive Medicine, University of Southern California, Arcadia, CA 91006, USA
* To whom correspondence should be addressed.
We develop a permutation test for assessing a difference in the areas under the curve (AUCs) in a paired setting where both modalities are given to each diseased and nondiseased subject. We propose that permutations be made between subjects specifically by shuffling the diseased/nondiseased labels of the subjects within each modality. As these permutations are made within modality, the permutation test is valid even if both modalities are measured on different scales. We show that our permutation test is a sign test for the symmetry of an underlying discrete distribution whose size remains valid under the assumption of equal AUCs. We demonstrate the operating characteristics of our test via simulation and show that our test is equal in power to a permutation test recently proposed by Bandos and others (2005).
Keywords: Area under the curve; Diagnostic test; Distribution-free test; Randomization test; Resampling; U-statistic
Received July 10, 2007; revised August 29, 2007; accepted for publication August 31, 2007.