# [BioC] Five variables, ABCDE, how to check whether (A-B)/(A-C) is equal to D/E?

Naomi Altman naomi at stat.psu.edu
Tue Aug 24 16:30:23 CEST 2010

```I think you need to explain whether ABCDE are measured on the same
individuals or are independent measurements.

Naomi

At 05:22 AM 8/24/2010, Weibo Xie wrote:
>Yes, you catch my thought completely. A solution I used is to enumerate all
>combination of A, B and C to obtain all possible values of (A-B)/(A-C) and
>also enumerate all combination of D and E to get all possible D/E, then
>apply Wilcoxon-Mann-Whitney rank test to compare these two groups of values.
>By this method, if the lengths of A,B,..,E are 5, then we will have
>5x5x5=125 values of (A-B)/(A-C) and  5x5=25 values of D/E. Such
>enumerated data may inflate the sample size and make the test more
>significant than the true. I don't know does it reasonable?
>
>-Weibo
>
>
>
>On Tue, Aug 24, 2010 at 4:41 PM, Moshe Olshansky <m_olshansky at yahoo.com>wrote:
>
> > Do you mean that A,B,...,E are same length and you want to apply t-test to
> > compare
> > (A-B)/(A-C) to D/E?
> > Technically this is straightforward, but even if A,B,...,E are normally
> > distributed, this is very much not true for (A-B)/(A-C) and D/E,
> so it won't
> > be appropriate to apply t-test (uness A,C and E are constants).
> >
> >
> > --- On *Tue, 24/8/10, Weibo Xie <xwbmail at gmail.com>* wrote:
> >
> >
> > From: Weibo Xie <xwbmail at gmail.com>
> > Subject: Re: [BioC] Five variables, ABCDE, how to check whether (A-B)/(A-C)
> > is equal to D/E?
> > To: "Moshe Olshansky" <m_olshansky at yahoo.com>
> > Cc: "Bioconductor" <bioconductor at stat.math.ethz.ch>
> > Received: Tuesday, 24 August, 2010, 6:09 PM
> >
> >
> >
> > Thanks for your quick reply! I think it's like 'equal means' in Two-Sample
> > t-Test.
> >
> >  -Weibo
> >
> > On Tue, Aug 24, 2010 at 3:58 PM, Moshe Olshansky
> <m_olshansky at yahoo.com<http://mc/compose?to=m_olshansky@yahoo.com>
> > > wrote:
> >
> > What exactly do you mean by "equal"?
> >
> > --- On Tue, 24/8/10, Weibo Xie
> <xwbmail at gmail.com<http://mc/compose?to=xwbmail@gmail.com>>
> > wrote:
> >
> > > From: Weibo Xie
> <xwbmail at gmail.com<http://mc/compose?to=xwbmail@gmail.com>
> > >
> > > Subject: [BioC] Five variables, ABCDE, how to check whether (A-B)/(A-C)
> > is equal to D/E?
> > > To: "Bioconductor"
> <bioconductor at stat.math.ethz.ch<http://mc/compose?to=bioconductor@stat.math.ethz.ch>
> > >
> > > Received: Tuesday, 24 August, 2010, 5:45 PM
> > > Hello everyone,
> > >
> > > I have 5 variables, denoted as A to E, each with several
> > > replicates. Is
> > > there a reasonable statistical test to check whether
> > > (A-B)/(A-C) is equal to
> > > D/E?
> > >
> > > Thanks for your help,
> > >
> > > -Weibo
> > >
> > >     [[alternative HTML version deleted]]
> > >
> > > _______________________________________________
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> > >
> >
> >
> >
>
>         [[alternative HTML version deleted]]
>
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Naomi S. Altman                                814-865-3791 (voice)
Associate Professor
Dept. of Statistics                              814-863-7114 (fax)
Penn State University                         814-865-1348 (Statistics)
University Park, PA 16802-2111

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