Greg Trafton <trafton at itd.nrl.navy.mil> writes:
Peter Dalgaard BSA <p.dalgaard at biostat.ku.dk> writes:
Greg Trafton <trafton at itd.nrl.navy.mil> writes:
summary(aov(rl ~ cond * session + Error(subj/(session)), data=mig))
Error: subj
Df Sum Sq Mean Sq F value Pr(>F)
cond 2 28.305 14.153 1.9916 0.2311
Residuals 5 35.531 7.106
Error: subj:session
Df Sum Sq Mean Sq F value Pr(>F)
session 2 4.4502 2.2251 2.9868 0.09616 .
cond:session 4 17.7335 4.4334 5.9509 0.01024 *
Residuals 10 7.4499 0.7450
---
Signif. codes: 0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1
(I ran this one this way b/c of a similar example from Baron's "Notes
for psychology experiments. Unfortunately, neither the session nor
the interaction cond:session are the same as SPSS's output, though the
degrees of freedom are correct in both, of course).
I'm certainly able to believe that SPSS is wrong and R is right, but
thought I'd check with this list to make sure I'm not doing something
completely stupid...
This is consistent with both lm() (using subj as a systematic effect) and lme(), so I'd strongly suspect that SPSS is getting it wrong. What does SPSS give?
OK, now I get to show off my ignorance of SPSS ;-) Perhaps I'm using it wrong, arg. I'm including the spool file and a word copy of it (which looks pretty ugly):
Argh. You have no idea how difficult it is to read that stuff when you're not on a Windows machine... But I suppose that converting it to plain text is a pain even *on* Windows. Anyways, as far as I can see, you are in fact getting the same interaction test (RL*COND, Sphericity Assumed, Type III SS=17.734), so I'd suspect that the test for the main effect is one of those weird things where you take the average over the three levels of cond, ignoring the fact that one level occurs twice as often as the others. What happens if you run the SPSS analysis without the interaction term?
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._