[R] pairwise.t.test for paired data

From: francogrex <francogrex_at_mail.com>
Date: Fri, 04 Apr 2008 08:20:31 -0700 (PDT)

Dear R-help, I have a question about pairwise.t.test and adjustment for multiple comparisons for paired data points. I have the following data:

n=c("x", "x", "x", "x", "x", "x", "x", "x", "x", "x", "y", "y", "y", "y", "y", "y", "y", "y", "y", "y", "z", "z", "z", "z", "z", "z", "z", "z", "z", "z")

and

d=c(3.38501220258169, 0.732526675324789, -0.638736410843593,

7.87414894080545, 
3.6341475242877, -2.80762187242111, 14.1405912463741, -9.29904247482419, 
9.8636915453275, 5.43287495347734, 12.2804612051493, 7.83975161028828, 
15.2200332220459, 6.72953902619773, 9.11557944514228, 9.79268012944973, 7.6112143261283, 10.3912598689021, 8.04934992955112, 13.3935024789408,
12.1276080143311, 11.2987640203845, 2.05386456839974, 12.8386335687123, 
3.84418682233211, 17.4626505871045, 6.5947625121599, -10.6664750811034, 
21.3346023277454, 4.99216977422232)

Then I do the tests

> pairwise.t.test(d,n,p.adjust="bonf",paired=F)

        Pairwise comparisons using t tests with pooled SD

data: d and n

  x y
y 0.092 -
z 0.326 1.000

P value adjustment method: bonferroni

Assuming the data are paired:

> pairwise.t.test(d,n,p.adjust="bonf",paired=T)

        Pairwise comparisons using t tests with pooled SD

data: d and n

  x y
y 0.092 -
z 0.326 1.000

P value adjustment method: bonferroni

I have no indication that the test is taking into account that the data are paired! Is it possible to do a pairwise t test with adjustement for multiple comparisons using pairwise.t.test? If not any other function for that? Thanks.

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Received on Fri 04 Apr 2008 - 16:55:38 GMT

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