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st: SEM & degrees of freedom
From
Daniel Coulombe <[email protected]>
To
<[email protected]>
Subject
st: SEM & degrees of freedom
Date
Fri, 20 Dec 2013 15:39:21 -0500
Hello,
Can anybody tell me why the number of degrees of freedom is the same for the
two following model specifications :
1: sem (Verbal@bv -> word similar) (NVerbal@bn -> matrices seq_quan)
(Spatial@bs -> pattern r_design), covstruct(_lexogenous, diagonal) stand
cov( NVerbal*Verbal Spatial*Verbal Spatial*NVerbal)
2: sem (Verbal -> word similar) (NVerbal -> matrices seq_quan) (Spatial ->
pattern r_design), covstruct(_lexogenous, diagonal) stand cov(
NVerbal*Verbal Spatial*Verbal Spatial*NVerbal)
In model 1, I constrain to equality the coefficients for each factors, thus
gaining 3 degrees of freedom over the unconstrained model 1. But when I run
these, I get 6 degrees of freedom for BOTH models!
LR test of model vs. saturated: chi2(6) = 29.28, Prob > chi2 = 0.0001
for model 1 DF should be equal to 9
LR test of model vs. saturated: chi2(6) = 9.76, Prob > chi2 = 0.1351
for model 2 DF is correct (at 6)
Thanks for any help!
Daniel Coulombe
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