[疑难问答]Mixed Model with Repeated Measures?

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收藏 2014-06-06

I am analyzing some data from a home visiting program.  Because there are repeated measures, and some of those measures are missing at random, the literature suggests that I use a mixed model analysis in spss.  I have some questions since I haven't done this before.

On the first slide (after analyze-mixed models-linear), I put in client ID as the subject variable and time as the repeated measure.  What would be the appropriate "repeated covariance type" on this slide?  I assume the repeated measure (nurturing assessment) would be correlated since the same assessment was given over time.

On the second slide I have put in time, primary language, and ethnicity as fixed factors.  What would I put in, if anything, for random effects?
I also want to study dosage (# of home visits per client) and how it effects nurturing---but it is a continuous variable.  How can I do this?  I've thought since the # varies from 2 to 72 home visits that I could categorize
the visits to low, medium, and high.  Would that be appropriate to enter as a fixed variable?

I do have number of months enrolled in the program and can enter that number in as a covariate.

Thanks

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ReneeBK

2014-6-6 23:00:48

*Generate Data.
set seed 65923454.

new file.
input program.
compute subject=-99.
compute group = -99.
leave subject to group.
loop subject= 1 to 1000.
loop group = 1 to 3.
compute y = rv.normal(0,1).
end case.
end loop.
end loop.
end file.
end input program.
execute.

USE ALL.
COMPUTE filter_$=(uniform(1)<=.95).
VARIABLE LABELS filter_$ 'Approximately 95% of the cases (SAMPLE)'.
FORMATS filter_$ (f1.0).
FILTER  BY filter_$.
EXECUTE.

IF  (filter_$=0) y=$SYSMIS.
EXECUTE.

delete variables filter_$.

MIXED y BY group
/FIXED=group  | SSTYPE(3)
/METHOD=REML
/PRINT=R
/REPEATED=group | SUBJECT(subject) COVTYPE(diag).

MEANS TABLES=y BY group
  /CELLS=VAR COUNT.

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