Check this box to perform the Sequence Kernel Association Test (SKAT) defined by Wu et al. (2011) ^{ 1 } .In this test, the variance component for all SNPs (or collapsed rare variant loci) with the same value of the Annotation Analysis Group Variable is tested for using a score statistic that follows a linear combination of chi-square distributions .The chi -square approximation given by Liu, Tang, and Zhang (2009) ^{ 2 } is used to calculate p-values for this test.
Wu, M.C., S. Lee, et al. (2011). Rare-variant association testing for sequencing data with the sequence kernel association test. American Journal of Human Genetics 89:82-93.
Liu, H., Y. Tang, and H.H. Zhang. (2009). A new chi-square approximation to the distribution of non-negative definite quadratic forms in non-central normal variables. Computational Statistics and Data Analysis 53:853-856.