Simple, robust linkage tests for affected sibs

Nonparametric analysis of affected sib pairs or other small sets of affected relatives provides a simple, robust method of linkage analysis. The shape of the constraint set for identity-by-descent (IBD) probabilities for sibs is related to the robustness of the affected-sib-pair tests. In addition, minmax tests are available that are more robust than the tests currently in use. The minmax tests' robustness is supported by asymptotic-power calculations.