ClippingRankSumTest

Rank Sum Test for hard-clipped bases on REF vs.

Overview

This variant-level annotation tests whether the data supporting the reference allele shows more or less base clipping (hard clips) than those supporting the alternate allele. The ideal result is a value close to zero, which indicates there is little to no difference. A negative value indicates that the reads supporting the alternate allele have more hard-clipped bases than those supporting the reference allele. Conversely, a positive value indicates that the reads supporting the alternate allele have fewer hard-clipped bases than those supporting the reference allele. Finding a statistically significant difference either way suggests that the sequencing and/or mapping process may have been biased or affected by an artifact.

Statistical notes

The value output for this annotation is the u-based z-approximation from the Mann-Whitney-Wilcoxon Rank Sum Test applied to base clips (number of hard-clipped bases on reads supporting REF vs. number of hard-clipped bases on reads supporting ALT). See the method document on statistical tests for a more detailed explanation of the ranksum test.

Caveat

The clipping rank sum test can not be calculated for sites without a mixture of reads showing both the reference and alternate alleles.