# W too high and interpretating results from collapsed/feature table **URL:** https://forum.qiime2.org/t/w-too-high-and-interpretating-results-from-collapsed-feature-table/21700 **Category:** User Support **Tags:** ancom **Created:** [December 20, 2021, 8:22pm UTC](https://forum.qiime2.org/t/w-too-high-and-interpretating-results-from-collapsed-feature-table/21700 "2021-12-20T20:22:39Z") **Posts on this page:** 1 **Showing post:** 3
### Author: ![mverce](https://forum.qiime2.org/letter_avatar_proxy/v4/letter/m/e68b1a/32.png) [@mverce](https://forum.qiime2.org/u/mverce) #### Post date: [January 6, 2022, 10:05am UTC](https://forum.qiime2.org/t/w-too-high-and-interpretating-results-from-collapsed-feature-table/21700/3 "2022-01-06T10:05:38Z")
Hi João and happy 2022! To detect likely differences in abundance, ANCOM is testing for significant differences in ASV ratios between groups. For each ASV, the number of "successful" tests like that is called W. This means that the maximum W equals the number of ASVs in your table minus 1, in your case 612 - 1 = 611 for the ASV table and 203 - 1 = 202 for the collapsed table. This also means that W values higher than in the tutorial are nothing to worry about and, in fact, you have taxa in your data set with significant differential abundance (even reaching maximum W). Regarding the x-axis, I only see negative and positive values (the classical volcano crater shape) when I compare exactly two groups. If I compare more than two groups, all clr values are positive, which is also what you see, so I think it is normal. I think the values are made positive during the calculation, but someone else may know why exactly that is. You may find the following threads useful: > [@ANCOM volcano plot - high W negative clr](https://forum.qiime2.org/t/ancom-volcano-plot-high-w-negative-clr/20899): > > Hi qiime2 community, I have a volcano plot interpretation question resulting from my ANCOM analysis Having ran ANCOM at the genus (level 6) and species level (7) comparing a control group to a lesion group . and it gave me interesting results: Treponema species has a high W – so they are standout taxa that qiime pointed out. These really high W-statistic numbers have negative clr – and I am unsure why that is. Does it actually mean it is decreasing in abundance across the categories? I was u… > [@ANCOM clr results confusion](https://forum.qiime2.org/t/ancom-clr-results-confusion/8794): > > Hello, I am having some confusion with my ANCOM results. From my understanding, the clr is like the fold-change and the 100% abundance shows the counts in each group. I would expect if I have group A and B then anytime I have more counts in A than B I would obtain either positive or negative clr’s consistently. But in my data set, I have two significant taxa that are both higher in group A than B, but one of them gives a negative clr while the other gives a positive clr. How is this possible? D… I hope that cleared some of your concerns! --- _[View the full topic](https://forum.qiime2.org/t/w-too-high-and-interpretating-results-from-collapsed-feature-table/21700)._