Hi Daren, >> Small progress, ...
m4 <- list(m1=m1, m2=m2, m3=m3) boxplot(m4) It's always a good idea to have a look at your data first (assuming you haven't). This shows that the reliable instrument is m2. HTH, Mark. Daren Tan wrote: > > > Small progress, I am relying on levene test to check for equality of > variances. Is my understanding correct, the larger the p-value, the more > likely the variances are the same ? > >> trt > [1] 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 > Levels: 1 2 3 4 >> levene.test(rep(rnorm(5), 4), trt, option="median") > > Modified Robust Brown-Forsythe Levene-type test based on the > absolute > deviations from the median > > data: rep(rnorm(5), 4) > Test Statistic = 0, p-value = 1 > > > >> From: [EMAIL PROTECTED] >> To: [EMAIL PROTECTED] >> Subject: How to solve this problem ? >> Date: Wed, 20 Aug 2008 13:33:23 +0000 >> >> >> I have disabled html text editing mode, thanks to Prof. Ripley for the >> kind reminder. >> >> Given three geological devices that takes 5 readings at 4 environmental >> conditions (A to D). What will be the proper approach to select the most >> reliable device ? >> >> m1 <- c(73,52,49,53,83,43,58,94,53,62,75,66,41,72,70,75,57,59,85,84) >> m2 <- c(31,38,30,35,36,26,27,38,22,31,24,35,36,31,38,33,32,28,33,30) >> m3 <- c(65,57,36,40,36,30,40,34,37,40,33,33,37,29,37,37,30,33,40,35) >> >> names(m1) <- rep(LETTERS[1:4], each=5) >> names(m2) <- rep(LETTERS[1:4], each=5) >> names(m3) <- rep(LETTERS[1:4], each=5) >> >> Before writing this email, I have tried to compare the sd for each device >> at each condition, but ran into obstacle on how to formulate the null >> hypothesis. Alternative solution tried was ANOVA, I am unsure whether it >> can help, as it compares the differences in means of each group. >> >> Thanks >> >> _________________________________________________________________ >> Easily edit your photos like a pro with Photo Gallery. >> http://get.live.com/photogallery/overview > > ______________________________________________ > 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. > > -- View this message in context: http://www.nabble.com/How-to-solve-this-problem---tp19069553p19084239.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.