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Sensitivity of two-sample permutation inferences in observational studies. (English) Zbl 0703.62060

In observational studies, subjects are not randomly assigned to treatment or control, so they may differ in their chances of receiving the treatment. A simple method is developed and demonstrated for displaying the sensitivity of conventional two-group permutation inferences to departures from random assignment of treatments. The unmatched case, discussed here, differs in certain technical and computational details from the matched case, discussed previously; however, the underlying model and the method for quantifying departures from randomization are the same. The method may be applied to Wilcoxon’s rank sum test, the Gehan and log-rank tests for censored outcomes, Mantel’s test for scored categories, and Fisher’s exact test for binary responses.

MSC:

62G10 Nonparametric hypothesis testing

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