Posted by
Beckstead, Jason-2 on
Mar 02, 2021; 2:49pm
URL: http://spssx-discussion.165.s1.nabble.com/GENLINMIXED-EMMEANS-don-t-agree-with-descriptives-tp5740214p5740235.html
Hi guys,
Thanks for your responses regarding GENLINMIXED. I believe that including the random intercepts in the model is necessary to account for the nested structure of the data (9 binary responses per subject) and which should adjust the standard errors for nonindependence in the data.
Also, because the DV is binary the binomial distribution with the logit link function is appropriate for conducting logistic regression. I think that specifying both of these options is necessary to obtain proper estimates of the 95% Cis for the cell means (which are proportions).
I also note that the estimated grand mean (also a proportion) does not equal that of the entire sample (as calculated using MEANS or DESCRIPTIVES).
At this point I am quite uneasy trusting the results from GENLINMIXED. Does anyone know of another way to estimate a multilevel logistic regression in SPSS.
Thanks,
Jason
_____________________________________________________________
Jason W. Beckstead, Ph.D.
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-----Original Message-----
From: SPSSX(r) Discussion <
[hidden email]> On Behalf Of Bruce Weaver
Sent: Saturday, February 27, 2021 9:28 PM
To:
[hidden email]
Subject: Re: GENLINMIXED EMMEANS don't agree with descriptives
"If you don't estimate random effects the two procedures match."
Aha. Good observation, Andy. However, to one of Jason's points, the limits of some CIs are < 0 or > 1. Using the small dataset Jason provided, and excluding random effects yields these EMMEANS:
Estimates
AC WT Mean Std. Error 95% Confidence Interval
Lower Upper
1 1 .167 .152 -.140 .473
2 .333 .192 -.054 .721
3 .333 .192 -.054 .721
2 1 .500 .204 .089 .911
2 .667 .192 .279 1.054
3 .667 .192 .279 1.054
3 1 .667 .192 .279 1.054
2 .833 .152 .527 1.140
3 .667 .192 .279 1.054
Andy W wrote
> Bruce, those should only change the standard error of the means, not
> the mean estimate itself (at least that is the case for data with only
> discrete dummy variables like here).
>
> Here I am not sure how SPSS treats the random effect in EMMEANS (sets
> it to
> 0 I imagine). If you don't estimate random effects the two procedures
> match.
>
> MEANS CHOICE BY AC BY WT.
>
> GENLINMIXED /DATA_STRUCTURE SUBJECTS=SUB /FIELDS TARGET=CHOICE
> TRIALS=NONE OFFSET=NONE /TARGET_OPTIONS DISTRIBUTION=BINOMIAL
> LINK=LOGIT REFERENCE=0 /FIXED EFFECTS= AC WT AC*WT USE_INTERCEPT=TRUE
> /EMMEANS TABLES=AC*WT /BUILD_OPTIONS TARGET_CATEGORY_ORDER=aSCENDING
> INPUTS_CATEGORY_ORDER=aSCENDING.
>
>
>
>
>
>
> -----
> Andy W
> apwheele@
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