Chunhao Tu <tu_chun...@yahoo.com> wrote >Hi R users, >My question is, If I have 3 groups, A, B, C and I know mean of A =20, B=21, >and C=20.5 and I also know the >standard error of A =1.1, B=2.2, C=3.2. Plus, I know A has 30 observations, >B has 78, C has 45. But I do not have the raw data. > >Can I use pairwise.t.test to conduct a Bonferroni test? If yes, Could you >give me a hint?
If the data in each group is normally distributed, you could use the mean and sd and N in rnorm and then test the results. But if you don't know that, then I think it's a bit up in the air. A - N = 30, sem = 1.1, mean = 20 sd = 1.1*30^.5 = 6.02 B - N = 78, sem = 2.2, mean = 21 sd = 2.2*78^.5 = 19.43 C - N = 45, sem = 3.2, mean = 20.5, sd = 3.2*45^.5 = 21.46 let's do just A and B, to keep it a bit simpler: if both are normal: A <- rnorm(n = 30, mean = 20, sd = 6.02) B <- rnorm(n = 78, mean = 21, sd = 19.43) t.test(A,B) t = .927 but if A is uniform and B is normal A <- rnorm(n = 30, mean = 20, sd = 6.02) B <- runif(n = 78, mean = 21, sd = 19.43) t.test(A,B) t = 0.42 HTH, and hope I didn't mess up one of the calculations due to insufficient caffeine intake Peter Peter L. Flom, PhD Statistical Consultant www DOT peterflomconsulting DOT 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.
