Re:[R] Correct contrast for unreplicated 2K factorial design

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From: Peter Ho (peter@fe.up.pt)
Date: Fri 27 Jun 2003 - 09:38:48 EST 

Message-id: <3EFB8408.8050006@fe.up.pt>

Hi all,

I have been trying to reproduce an analysis from Douglas Montgomery´s
book on design and analysis of experiments. Table 6.10 of example 6.2 on
page 246, gives a table as follows:

> NPK <- expand.grid(A=mp,B=mp,C=mp,D=mp)
> Rate <- c(45,71,48,65,68,60,80,65,43,100,45,104,75,86,70,96)
> filtration <- cbind(NPK,Rate)
> filtration
   A B C D Rate
1 - - - - 45
2 + - - - 71
3 - + - - 48
4 + + - - 65
5 - - + - 68
6 + - + - 60
7 - + + - 80
8 + + + - 65
9 - - - + 43
10 + - - + 100
11 - + - + 45
12 + + - + 104
13 - - + + 75
14 + - + + 86
15 - + + + 70
16 + + + + 96

Two additional tables follow. Table 6-11 for contracts constants and
Table 6-12 for Factor effects estimates.
So far my attempts at fitting the model gives me very different effect
estimates. This I guess is because I have not set the right contrasts?
Can anyone explain to me how I could set the correct contrasts in R to
estimate the effects in this unreplicated 2^4 factorial?

Thanks in advance,

Peter

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