[R] Nested ANOVA residuals error

Bert Gunter
Thu, 16 Jul 2009 20:08:41 -0000

Hint: You have 27 observations fit by 27 fixed effects (including the mean).


You need to consult a statistician, as you seem not to have the basic
statistical understanding required. Person should be a random effect. Was
this a homework problem, perchance?

Bert Gunter
Genentech Nonclinical Biostatistics

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Jeff DaCosta
Sent: Thursday, July 16, 2009 12:37 PM
To: r-help at r-project.org
Subject: [R] Nested ANOVA residuals error

I am having trouble setting up a nested anova model.  Here is a
truncated version of my data:

 > data
      Ind Treatment         PC1
1  PER14        SC  1.14105282
2  PER14        SH  1.45348615
3  PER14        AC  2.45096904
4  PER25        SC  1.23687887
5  PER25        SH  4.54797450
6  PER25        AC -0.73391131
7  PER30        SC  1.15899433
8  PER30        SH  2.83273736
9  PER30        AC -0.86272186
10 PER31        SC  1.90495285
11 PER31        SH  5.68514429
12 PER31        AC -2.25110314
13 PER35        SC  2.16463279
14 PER35        SH  1.69053389
15 PER35        AC  1.87528942
16 PER36        SC -2.44795781
17 PER36        SH -3.59415298
18 PER36        AC  1.90756192
19 PER41        SC -2.83086573
20 PER41        SH  4.26803170
21 PER41        AC  2.42548862
22 PER48        SC -1.86403368
23 PER48        SH -0.08713013
24 PER48        AC -1.98056853
25 PER52        SC  2.35012436
26 PER52        SH -2.19384500
27 PER52        AC  1.38686223

 > str(data)
'data.frame':	27 obs. of  3 variables:
  $ Ind      : Factor w/ 9 levels "PER14","PER25",..: 1 1 1
2 2 2 3 3
3 4 ...
  $ Treatment: Factor w/ 3 levels "AC","SC","SH":
2 3 1 2 3 1 2 3 1
2 ...
  $ PC1      : num  1.14 1.45 2.45 1.24 4.55 ...

PC1 is my response variable, and Treatment is my factor with three
levels.  Each  of the nine individuals (Ind) in the study was tested
for all three factor levels, so I want to run the model with Ind
nested in Treatment.  I think that I want to set up the model like this:

 > m1<-aov(PC1~Treatment/Ind))

but I get the following error with anova(m1), and am not sure why I
get zero for all the residuals.
 > anova(m1)
Analysis of Variance Table

Response: PC1
               Df  Sum Sq Mean Sq F value Pr(>F)
Treatment      2   9.215   4.607
Treatment:Ind 24 142.140   5.923
Residuals      0   0.000
Warning message:
In anova.lm(m1) :
   ANOVA F-tests on an essentially perfect fit are unreliable

Any input would be appreciated, thanks for your time and consideration.
-Jeff
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