Date:         Fri, 23 Jul 2010 11:17:42 -0500
Reply-To:     Alex Reutter <areutter@us.ibm.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Alex Reutter <areutter@us.ibm.com>
Subject:      Re: Mixed model ANOVA degrees of freedom
In-Reply-To:  <AANLkTim2MLIntftGnU_eyHjDxt-6ILJhT3Jl8SOcMRfO@mail.gmail.com>
Content-Type: multipart/alternative;

The denominator df are computed using Satterthwaite's approximation.  More
details are in the MIXED algorithms documentation (Help > Algorithms).

Alex



From:
Kambiz <ktavabi@googlemail.com>
To:
SPSSX-L@LISTSERV.UGA.EDU
Date:
07/22/2010 06:33 PM
Subject:
Mixed model ANOVA degrees of freedom
Sent by:
"SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>



Typically when reporting test results from a GLM I use  the format
(F(df_factor_term,df_error_term)=F-stat, p=p-value), i.e.,
(F(n,n-1)=statistic,p=pvalue). My question is what is the equivalent
format for a reporting results from a linear mixed model. For example
if I have a fixed effect for term X SPSS outputs numerator and
denominator degrees of freedom(df), I am assuming that
F(df_numerator,df_denominator) is equivalent to
F(df_factor_term,df_error_term), and in both instances the
significance level for the F is from the F distribution with the
degrees of freedom for the numerator and denominator mean squares. If
that is correct, why does the denominator df in the mixed model not
take on the value of n-1(or some constant, where n=number of factor
levels)? Thanks in advance for your comments.

--
-K.

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