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| joz posted on Saturday, July 18, 2020 - 8:49 am
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I am using DSEM without random slopes (T is small; N large).
I am testing effect of gadT1 on gadT2 through possible mediators: NA, PA, logRVNA logRVPA
I wish to control for phqT1 in all mediation. phqT1 is strongly correlated with gadT1.
1) From previous threads, I read you must add control variable to all ON statements.
so is the syntax below correct?
2) since phq and gad are strongly correlated, should I put gadT2 WITH phq? or leave out if putting PHQ on all ON statements?
ANALYSIS:
TYPE = TWOLEVEL RANDOM;
Estimator = BAYES;
PROC = 2;
BITER = (5000);
THIN = 10;
MODEL:
%WITHIN%
PA ON PA&1;
logRVPA|PA;
PA ON NA&1;
NA ON PA&1;
NA ON NA&1;
logRVNA|NA;
%BETWEEN%
GAD_T1 GAD_T2 PHQ9_T1;
PA NA logRVNA logRVPA on GAD_T1 PHQ9_T1 (a1-a8);
GAD_T2 on PA NA logRVNA logRVPA GAD_T1 PHQ9_T1 (b1-b6);
MODEL CONSTRAINT:
new(ab_PAg); ab_PAg = a1*b1;
new(ab_NAg); ab_NAg = a2*b2;
new (ab_logRVNAg); ab_logRVNAg = a3*b3;
new (ab_logRVPAg); ab_logRVPAg = a4*b4;
new(ab_PAp); ab_PAp = a5*b1;
new(ab_NAp); ab_NAp = a6*b2;
new (ab_logRVNAp); ab_logRVNAp = a7*b3;
new (ab_logRVPAp); ab_logRVPAp = a8*b4; |
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I hope you have T at least > 10.
1) Yes.
2) I would leave out phq |
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| joz posted on Tuesday, August 04, 2020 - 3:44 pm
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| Thank you very much! As shown above, I am doing DSEM without random slopes because my T is small (around 10). Is there any benefit to using DSEM in this case? Would regular multilevel SEM mediation on Mplus give the same result? |
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| When T is small, I would not use random variance. In fact, I would not use DSEM for T < 10 but instead use regular modeling. |
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| joz posted on Tuesday, August 04, 2020 - 7:43 pm
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| Thank you! To clarify, when you say to use regular modeling for T <10, do you mean regular multilevel SEM modeling, or regular multilevel modeling? |
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| Either one. And single-level wide modeling is also an alternative here. |
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| joz posted on Thursday, August 06, 2020 - 12:39 pm
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Ok. Thanks for suggestion for regular modeling instead of DSEM given T<10, N is large. I completed the mediation analysis with multilevel SEM because I had Level 2 mediation (code is below).
Turns out the MSEM multilevel mediation results were almost identical to DSEM multilevel mediation.
Questions:
1) Given DSEM multilevel mediation results were almost identical to MSEM, what is the drawback to using DSEM mediation results?
2) Since MSEM is suggested alternative to DSEM, I want to do lagged analysis with MSEM (previous occasion predicting subsequent). Given T<10, I will not do random slopes. Can I do lagged WITHIN person analysis with MSEM?
2)Is there a benefit to doing MSEM multilevel mediation analysis with Bayesian estimation instead of the default?
ANALYSIS:
TYPE = TWOLEVEL RANDOM;
MODEL:
%WITHIN%
PA
NA
%BETWEEN%
PHQ9_T1 PHQ9_T2;
PHQ9_T2 on PHQ9_T1;
PA NA on PHQ9_T1 (a1-a2);
PHQ9_T2 on PA NA (b1-b2);
PHQ9_T2 on PHQ9_T1;
GAD_T1 GAD_T2;
GAD_T2 on GAD_T1;
PA NA on GAD_T1 (a3-a4);
GAD_T2 on PA NA (b3-b4);
MODEL CONSTRAINT:
new(ab_PA); ab_PA = a1*b1;
new(ab_NA); ab_NA = a2*b2;
new(ab_PAg); ab_PAg = a3*b3;
new(ab_NAg); ab_NAg = a4*b4; |
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Mplus MSEM cannot handle auto-regressions. To handle AR, you would have to do it in single-level wide format. In the twolevel setting with Mplus, only DSEM can handle AR.
1) I would have to see both model outputs to say. Simulations show that DSEM produces good results with T=10 only if you have a very simple DSEM model.
2) Answered above.
3) Using Bayes, it is easier to get non-symmetric CIs which may be needed. They are obtained automatically in the Bayes framework. |
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| joz posted on Friday, August 07, 2020 - 8:10 am
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| Ok, for 1) I sent both model outputs to support, with my license number. Thank you for your help! |
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