Posted by
Zdaniuk, Bozena-3 on
Mar 24, 2021; 9:14pm
URL: http://spssx-discussion.165.s1.nabble.com/Interpretation-of-interaction-with-time-varying-predictor-Growth-model-tp5740294p5740346.html
Hi Oliver,
I did longitudinal mediation analysis where I looked at changes in one variable mediating changes in the outcome (mediator and outcome were concurrent) in response to treatment. I used subject centered Level-1 scores as indicators of change for both the mediator and the outcome. Happy to send you a reference directly if you are interested.
Cheers,
Bozena
-----Original Message-----
From: SPSSX(r) Discussion <
[hidden email]> On Behalf Of Oliver
Sent: March 24, 2021 6:49 AM
To:
[hidden email]
Subject: Re: Interpretation of interaction with time-varying predictor (Growth model)
[CAUTION: Non-UBC Email]
Hi everyone,
I thought about something related to my previous question related to the inclusion of a time-varying moderator (i.e., dep; 0-10) in a model that examines the effect of time (IV; categorical) on the outcome (pain; 0-10).
The Level 1 (Time * dep) interaction is significant, but I want to interpret this effect. Results suggest that the degree of within-person changes in pain across time points varies as a function of concurrent/within-person changes in the moderator across time points,
For data interpretation/data vizualization, perhaps it could be reasonable to determine values that correspond to +/- 1SD based on the cluster/within-person centered scores on the moderator ? These values (i.e.,
+/- 1SD) would be derived based on the grand-mean of centered scores
+(only
way, I guess), but perhaps this could still be a useful approach ? The EMMEANS line could look like this:
MIXED Pain BY Time WITH c_Dep
/METHOD = REML
/PRINT = SOLUTION TESTCOV
/FIXED = Time c_Dep Time * c_Dep | SSTYP(3) /RANDOM = INTERCEPT | SUBJECT(ID) COVTYPE(UN) /REPEATED = Wave | SUBJECT(ID) COVTYPE(AR1) /EMMEANS TABLES(TimeC) WITH(c_dep = -0.91) COMPARE(TimeC) ADJ(SIDAK) /EMMEANS TABLES(TimeC) WITH(c_dep = 0) COMPARE(TimeC) ADJ(SIDAK) /EMMEANS TABLES(TimeC) WITH(c_dep = 0.91) COMPARE(TimeC) ADJ(SIDAK).
Thanks in advance for your input!
O.
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