Reading the original post it was clear to me that the poster was looking for a test of equivalence, but obviously there was room for interpretation!
albyn On Mon, Feb 14, 2011 at 09:46:13AM -0700, Greg Snow wrote: > Reading the original post it is fairly clear that the original poster's > question does not match with the traditional test of equivalence, but rather > is trying to determine "distinguishable or indistinguishable". If the test > in my suggestion is statistically significant (and note I did not suggest > only testing the interaction) then that meets one possible interpretation of > "distinguishable", a non-significant result could mean either equivalence or > low power, the combination of which could be an interpretation of > "indistinguishable". > > I phrased my response as a question in hopes that the original poster would > think through what they really wanted to test and get back to us with further > details. It could very well be that my response is very different from what > they were thinking, but explaining how it does not fit will better help us > understand the real problem. > > -- > Gregory (Greg) L. Snow Ph.D. > Statistical Data Center > Intermountain Healthcare > greg.s...@imail.org > 801.408.8111 > > > > -----Original Message----- > > From: Albyn Jones [mailto:jo...@reed.edu] > > Sent: Sunday, February 13, 2011 9:53 PM > > To: Greg Snow > > Cc: syrvn; r-help@r-project.org > > Subject: Re: [R] Test for equivalence > > > > testing the null hypothesis of no interaction is not the same as a > > test of equivalence for the two differences. There is a literature on > > tests of equivalence. First you must develop a definition of > > equivalence, for example the difference is in the interval (-a,a). > > Then, for example, you test the null hypothesis that the difference > > is in [a,inf) or (-inf,-a] (a TOST, or two one sided tests). One > > simple procedure: check to see if the 90% CI for the difference > > (difference of the differences or the interaction effect) is contained > > in the interval (-a,a). > > > > albyn > > > > Quoting Greg Snow <greg.s...@imail.org>: > > > > > Does it make sense for you to combine the 2 data sets and do a 2-way > > > anova with treatment vs. control as one factor and experiment number > > > as the other factor? Then you could test the interaction and > > > treatment number factor to see if they make a difference. > > > > > > -- > > > Gregory (Greg) L. Snow Ph.D. > > > Statistical Data Center > > > Intermountain Healthcare > > > greg.s...@imail.org > > > 801.408.8111 > > > > > > > > >> -----Original Message----- > > >> From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > > >> project.org] On Behalf Of syrvn > > >> Sent: Saturday, February 12, 2011 7:30 AM > > >> To: r-help@r-project.org > > >> Subject: [R] Test for equivalence > > >> > > >> > > >> Hi! > > >> > > >> is there a way in R to check whether the outcome of two different > > >> experiments is statistically distinguishable or indistinguishable? > > More > > >> preciously, I used the wilcoxon test to determine the differences > > >> between > > >> controls and treated subjects for two different experiments. Now I > > >> would > > >> like to check whether the two lists of analytes obtained are > > >> statistically > > >> distinguishable or indistinguishable > > >> > > >> I tried to use a equivalence test from the 'equivalence' package in > > R > > >> but it > > >> seems that this test is not applicable to my problem. The test in > > the > > >> 'equivalence' package just determines similarity between two > > conditions > > >> but > > >> I need to compare the outcome of two different experiments. > > >> > > >> My experiments are constructed as follows: > > >> > > >> Exp1: > > >> 8 control samples > > >> 8 treated samples > > >> -> determine significantly changes (List A) > > >> > > >> Exp2: > > >> 8 control samples > > >> 8 treated samples > > >> -> determine significantly changes (List B) > > >> > > >> > > >> Now i would like to check whether List A and List B are > > distinguishable > > >> or > > >> indistinguishable. > > >> > > >> Any advice is very much appreciated! > > >> > > >> Best, > > >> beginner > > >> -- > > >> View this message in context: http://r.789695.n4.nabble.com/Test- > > for- > > >> equivalence-tp3302739p3302739.html > > >> Sent from the R help mailing list archive at Nabble.com. > > >> > > >> ______________________________________________ > > >> R-help@r-project.org mailing list > > >> https://stat.ethz.ch/mailman/listinfo/r-help > > >> PLEASE do read the posting guide http://www.R-project.org/posting- > > >> guide.html > > >> and provide commented, minimal, self-contained, reproducible code. > > > > > > ______________________________________________ > > > R-help@r-project.org mailing list > > > https://stat.ethz.ch/mailman/listinfo/r-help > > > PLEASE do read the posting guide http://www.R-project.org/posting- > > guide.html > > > and provide commented, minimal, self-contained, reproducible code. > > > > > > > > -- Albyn Jones Reed College jo...@reed.edu ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
