Changing parameter reference - SPSS MIXED

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Changing parameter reference - SPSS MIXED

Eliz Connors
Hi,

I'm running the MIXED command on SPSS 26. I have three time points (Time),
two categorical fixed effects (POSTagencyR and age) and one continuous fixed
effect (years of experience, yrsexper).

I would like to know how to edit my code to change the reference parameter
for categorical variables displayed in the Estimates of Fixed Effects table.

I know how to set the desired reference category on the /emmeans statement
(see below) but would like to see the parameter estimates in my Estimates of
Fixed Effects table to match. For example, I have 3 time points and am
setting refcat (FIRST) to have time 2 and time 3 compared to time 1 in
pairwise comparisons. However, my Estimates of Fixed Effects table is
automatically setting time 3 parameter to zero "because it is redundant". Is
there a way to change the reference category for my categorical fixed
effects?

MIXED ASAPRS by POSTagencyR age Time WITH yrsexper
/FIXED POSTagencyR age Time yrsexper
/RANDOM intercept | subject(ID)
/REPEATED Time | subject(ID) covtype (ar1)
/emmeans = tables (POSTagencyR) compare (POSTagencyR) refcat (FIRST) ADJ
(LSD)
/emmeans = tables (Time) compare (Time) refcat (FIRST) ADJ (LSD)
/emmeans = tables (age) compare (age) refcat (FIRST) ADJ (LSD)
/print = solution.

Thank you for any guidance you can provide!





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Re: Changing parameter reference - SPSS MIXED

ChrisKeran
I assume you would need to first dummy code the categorical variable and then
include in your model all but the reference category. That is how I did this
with a logistic regression, BUT not sure about using this method with MIXED.



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Re: Changing parameter reference - SPSS MIXED

Bruce Weaver
Administrator
Alternatively, you could temporarily recode Time setting 1 = 4 (or some
higher number).  E.g.,


* Temporarily recode Time setting 1 = 4.
* Then in MIXED command, set REFCAT to LAST for Time.

TEMPORARY.
RECODE Time (1=4) (ELSE=COPY).

MIXED ASAPRS by POSTagencyR age Time WITH yrsexper
/FIXED POSTagencyR age Time yrsexper
/RANDOM intercept | subject(ID)
/REPEATED Time | subject(ID) covtype (ar1)
/emmeans = tables (POSTagencyR) compare (POSTagencyR) refcat (FIRST) ADJ
(LSD)
/emmeans = tables (Time) compare (Time) refcat (LAST) ADJ (LSD)
/emmeans = tables (age) compare (age) refcat (FIRST) ADJ (LSD)
/print = solution.




ChrisKeran wrote

> I assume you would need to first dummy code the categorical variable and
> then
> include in your model all but the reference category. That is how I did
> this
> with a logistic regression, BUT not sure about using this method with
> MIXED.
>
>
>
> --
> Sent from: http://spssx-discussion.1045642.n5.nabble.com/
>
> =====================
> To manage your subscription to SPSSX-L, send a message to

> LISTSERV@.UGA

>  (not to SPSSX-L), with no body text except the
> command. To leave the list, send the command
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> For a list of commands to manage subscriptions, send the command
> INFO REFCARD





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