Question: "Mixed" in romer output
0
18 months ago by
johnmcma10
johnmcma10 wrote:

Hi,

The output of romer in limma includes a field called "Mixed." The man page defines it as "[...]p-values for the alternative hypotheses mixed[...]", but neither paper cited mention what that alternate hypothesis actually means. Can anyone enlighten me as to what that p-value actually means?

Best regards,
John Ma, PhD
University of Texas MD Anderson Cancer Center

limma romer • 245 views
modified 18 months ago by James W. MacDonald51k • written 18 months ago by johnmcma10
2
18 months ago by
United States
James W. MacDonald51k wrote:

Is your question biological or statistical? If the latter, it seems pretty clear from the help page you reference:

     In the output, p-values are given for each set for three possible
alternative hypotheses. The alternative "up" means the genes in
the set tend to be up-regulated, with positive t-statistics. The
alternative "down" means the genes in the set tend to be
down-regulated, with negative t-statistics. The alternative
"mixed" test whether the genes in the set tend to be
differentially expressed, without regard for direction. In this
case, the test will be significant if the set contains mostly
large test statistics, even if some are positive and some are
negative. The first two alternatives are appropriate if you have a
prior expection that all the genes in the set will react in the
same direction. The "mixed" alternative is appropriate if you know
only that the genes are involved in the relevant pathways, without
knowing the direction of effect for each gene.

And now, after re-reading it, I would say it pretty well covers the biological interpretation as well. Is there something here that you find unclear?