Thank you all for your helpful responses. I apologize for the lack of
subject line. That is certainly not my habit. It happened because my
first email was refused because it was sent using an incorrect "From:"
line (an aliases email address, daniel.wagen...@uc.edu) instead of the
address I subscribed to the list with. When I resent it, I failed to
copy the subject line. My apologies.
- Daniel
On 10/30/2015 03:12 PM, Kevin Wright wrote:
Maybe you want
summary(aov(Y ~ A + Error(A:B)))
Kevin
On Fri, Oct 30, 2015 at 9:32 AM, Wagenaar, Daniel (wagenadl)
<wagen...@ucmail.uc.edu <mailto:wagen...@ucmail.uc.edu>> wrote:
Dear R users:
All textbook references that I consult say that in a nested ANOVA
(e.g., A/B), the F statistic for factor A should be calculated as
F_A = MS_A / MS_(B within A). But when I run this simple example:
set.seed(1)
A = factor(rep(1:3, each=4))
B = factor(rep(1:2, 3, each=2))
Y = rnorm(12)
anova(lm(Y ~ A/B))
I get this result:
Analysis of Variance Table
Response: Y
Df Sum Sq Mean Sq F value Pr(>F)
A 2 0.4735 0.23675 0.2845 0.7620
A:B 3 1.7635 0.58783 0.7064 0.5823
Residuals 6 4.9931 0.83218
Evidently, R calculates the F value for A as MS_A / MS_Residuals.
While it is straightforward enough to calculate what I think is the
correct result from the table, I am surprised that R doesn't give me
that answer directly. Does anybody know if R's behavior is
intentional, and if so, why? And, perhaps most importantly, how to
get the "textbook" result in the most straightforward way? (I'd like
to be able to give me students a simple procedure...)
Thanks,
Daniel Wagenaar
--
Daniel A. Wagenaar, PhD
Assistant Professor
Department of Biological Sciences
McMicken College of Arts and Sciences
University of Cincinnati
Cincinnati, OH 45221
Phone: +1 (513) 556-9757
Email: daniel.wagen...@uc.edu <mailto:daniel.wagen...@uc.edu>
Web: http://www.danielwagenaar.net
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Kevin Wright
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