[R] Dunnett's T3 test (DTK package) problem
Sam Mak
smak at gfz-potsdam.de
Mon Jul 1 14:45:01 CEST 2013
Hello,
I would like to ask a question about using DTK.test() to do the T3 test.
The data file is downloadable here:
http://ubuntuone.com/0zBl8QgUg1lAG6iK1CUicD
My question is: in the result of T3 test, is it possible for the following
three statements to hold without conflict?
1. m_a and m_b to be significantly different
2. m_a and m_c are not significantly different.
3. (m_c - m_a) >= (m_c- m_b)
where m_i is the mean value of group i.
I know that for Tukey test, the above three statements can't hold without
conflict.
The code to run the test is:
======== BEGIN ============
library(DTK)
df <- read.csv("./tmpData.csv")
DTK_result <- DTK.test(df$measurement, df$model, .05)
print(DTK_result)
======== END ============
Part of the result is displayed below. It says model05 and model01 are
significantly different, while model04 and model01 are not.
======== BEGIN ============
Diff Lower CI Upper CI
model02-model01 0.068468884 -0.04765040 0.1845882
model03-model01 0.143238920 -0.05589008 0.3423679
model04-model01 0.149002642 0.02900301 0.2690023
model05-model01 0.151504289 -0.04775209 0.3507607
model06-model01 0.193093625 0.07023934 0.3159479
...
======== END ============
The mean value of the groups are shown below. It shows (m_5 - m_1) > (m_4 -
m_1), where m_i is the mean value of model i.
======== BEGIN ============
library(plyr)
ddply(df, ~model, summarise, mean=mean(measurement))
model mean
1 model01 0.5352273
2 model02 0.6036962
3 model03 0.6784662
4 model04 0.6842300
5 model05 0.6867316
6 model06 0.7283210
7 model07 0.7489938
8 model08 0.7941213
9 model09 0.7944798
10 model10 1.1399370
11 model11 1.2582504
12 model12 1.2928783
13 model13 1.5789970
======== END ============
--
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