random effect model in GLM

random effect model in GLM

Post by William Dudle » Thu, 10 Sep 1998 04:00:00



I am trying to run a one way anova with a single random effect.
The independent variable (Group) has three levels.
Nested within each Group are 4 to 5 sites with about 50 - 60 subjects in
each site.

I am considering site as a random variable because we have randomly selected
(and assigned to conditions) these sites from a
larger sampling frame.

I am using the following syntax.

UNIANOVA
 wgt_tot   BY group site
  /RANDOM = site
  /METHOD = SSTYPE(3)
  /INTERCEPT = INCLUDE
  /EMMEANS = TABLES(group)
  /EMMEANS = TABLES(site)
  /EMMEANS = TABLES(group*site)
  /PRINT = DESCRIPTIVE
  /CRITERIA = ALPHA(.05)
  /DESIGN = group site group*site .

The output shows zero degrees of freedom for my "group" variable.  I wonder
if anyone has suggestions about what I am doing wrong.
(I have run the same syntax without the interaction and have the same problem).

TIA

Bill

William N Dudley, PhD
Asst Professor
Dept Behavi*Science and Health Education
Rollins School of Public Health
Emory University
Atlanta 30322
Phone 404 727 2447
FAX   404 727 1369

 
 
 

random effect model in GLM

Post by Theo Broekma » Thu, 10 Sep 1998 04:00:00


William your random affect is nested within your group variable so you
should specify that is the design:

/design = site within group group .

This gives you SS of the group effect and the site within group effect as
well as the variance components. I don.t know your data and research
questions, but in my opion you should consider the subjects as a random
effect within the groups, and the group as a fixed effect. The fact that the
groups were random sampled doesn't imply they are a random effect in your
analysis.

so your design would look something like
/design subject with group site group site by group.
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Quote:>I am trying to run a one way anova with a single random effect.
>The independent variable (Group) has three levels.
>Nested within each Group are 4 to 5 sites with about 50 - 60 subjects in
>each site.

>I am considering site as a random variable because we have randomly
selected
>(and assigned to conditions) these sites from a
>larger sampling frame.

>I am using the following syntax.

>UNIANOVA
> wgt_tot   BY group site
>  /RANDOM = site
>  /METHOD = SSTYPE(3)
>  /INTERCEPT = INCLUDE
>  /EMMEANS = TABLES(group)
>  /EMMEANS = TABLES(site)
>  /EMMEANS = TABLES(group*site)
>  /PRINT = DESCRIPTIVE
>  /CRITERIA = ALPHA(.05)
>  /DESIGN = group site group*site .

>The output shows zero degrees of freedom for my "group" variable.  I wonder
>if anyone has suggestions about what I am doing wrong.
>(I have run the same syntax without the interaction and have the same
problem).

>TIA

>Bill

>William N Dudley, PhD
>Asst Professor
>Dept Behavi*Science and Health Education
>Rollins School of Public Health
>Emory University
>Atlanta 30322
>Phone 404 727 2447
>FAX   404 727 1369


 
 
 

random effect model in GLM

Post by Frank Da » Fri, 11 Sep 1998 04:00:00


I tried to load the SPSS Student Version 8.0 for windows.   I got to
updating system registry when I got a stack dump that said _Ins0432.
What's happening?

Frank.