[R] pairwise.t.test

[Thomas Chesney]

I'm using pairwise.t.test() with 6 groups, but the dataset the 6 groups are in actually contains 24 groups.

When I run the test with all 24 groups the results I'm getting between Group 1 and Group 2 are very different from the results I'm getting between Group 1 and Group 2 when I split off the 6 groups and run the test. When only 6 groups are included the results are highly significant but with all 24 groups the results are insignificant.

I'm not adjusting p.values. The code I'm running is:

res <- pairwise.t.test(dat$Adopt, dat$Group, p.adj="none")

I thought the above code would run exactly the same test on Groups 1 and 2, regardless of how many groups are in the dataset. Can anyone explain what's going on?

Thank you,

Thomas Chesney




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