In relation to the discussion started by David Airey
<[email protected]> I had pointed out that it did not
matter if you used a numbering scheme such as
A 1 1 1 2 2 2
B 1 2 3 1 2 3
or
A 1 1 1 2 2 2
B 1 2 3 4 5 6
when dealing with B nested in A (written B|A in -anova- syntax).
I pointed to the discussion of this on page 64 of "[R] anova".
David Airey <[email protected]> then presents two data
sets with different labeling for the nested term and shows that
they produce different results.
Let me point out the misunderstanding between what I was saying
and the two datasets presented by David. David's first dataset
looks like:
neuron subject treatm~t measure
1. 1 1 1 1.232982
2. 2 1 1 1.166421
3. 3 1 1 1.674022
4. 1 1 2 1.690412
5. 2 1 2 1.079583
6. 3 1 2 1.983932
7. 1 1 3 -1.573235
8. 2 1 3 2.714028
9. 3 1 3 3.24
10. 1 1 4 1.470877
11. 2 1 4 4.342456
12. 3 1 4 .1263056
13. 1 1 5 3.049922
14. 2 1 5 2.537046
15. 3 1 5 -.7629604
16. 1 2 1 -1.013575
17. 2 2 1 .6785818
18. 3 2 1 -1.619054
19. 1 2 2 1.396539
20. 2 2 2 .9016123
21. 3 2 2 -2.113595
...
and his second looks like:
neuron subject treatm~t measure
1. 1 1 1 3.588527
2. 2 1 1 2.431523
3. 3 1 1 1.267083
4. 4 1 2 2.137298
5. 5 1 2 1.644081
6. 6 1 2 4.000641
7. 7 1 3 2.452223
8. 8 1 3 2.811015
9. 9 1 3 2.97793
10. 10 1 4 1.751251
11. 11 1 4 3.431399
12. 12 1 4 .4201414
13. 13 1 5 1.742686
14. 14 1 5 .4739965
15. 15 1 5 1.596641
16. 16 2 1 -.9146303
17. 17 2 1 -.5972514
18. 18 2 1 -1.519495
19. 19 2 2 -.6959237
20. 20 2 2 -.3078359
21. 21 2 2 -.5360426
...
His anova model is:
anova measure subject / neuron|subject ...
where I put ... so that we can focus on the first part of the
syntax that is the important part for this discussion.
It is not surprising that the 2 numbering schemes shown by David
are not producing the same results. If you look at my little
numbering scheme example
A 1 1 1 2 2 2
B 1 2 3 1 2 3
versus
A 1 1 1 2 2 2
B 1 2 3 4 5 6
which I claim will produce the same results for B|A, you will
notice that in the first case the numbering for B is 1 to n
within each level of A. The first dataset that David presents
has neuron with 1 to 3 repeated many times for the SAME subject.
If his numbering scheme for neuron went from 1 to 15 within each
subject, then it would produce the same results as his second
data set.
I hope this clarifies the point I was trying to make about
numbering schemes for nested ANOVA models. If not, please email
me and I will gladly discuss it with you.
Ken Higbee [email protected]
StataCorp 1-800-STATAPC
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