Posted by
Beckstead, Jason-2 on
Feb 27, 2021; 3:27pm
URL: http://spssx-discussion.165.s1.nabble.com/GENLINMIXED-EMMEANS-don-t-agree-with-descriptives-tp5740214p5740226.html
Bruce,
Thanks for your reply. One reason I am using binomial dist & logit link function is that the DV (Choice) is binary and so logistic regression (not linear regression) is appropriate.
Another reason is that I want the 95% CIs for the cell means (which are proportions).
Treating the DV as scale, as you suggest, gives CIs that are incorrect; they exceed the range (0 to 1) allowed for proportions. (as shown in the output from your suggested syntax)
SO, I guess my main question is what is GENLINMIXED actually doing as it calculates the estimated means, standard errors, & CIs using binomial dist & logit link function?
I have reviewed the algorithms documentation for GENLINMIXED, but haven't been able to make much sense of it.
My hunch is that when GENLINMIXED calculates EMMEANS, that some Ss are given more weight than others.
Any thoughts?
Jason
_____________________________________________________________
Jason W. Beckstead, Ph.D.
Professor/Quantitative Methodologist
University of South Florida College of Public Health
13201 Bruce B. Downs Blvd., MDC56, Tampa, FL 33612, USA
Statistical Editor, International Journal of Nursing Studies
phone: +1.813.974.7667 fax: +1.813.974.4719
International Journal of Nursing Studies
http://www.elsevier.com/ijns NOTE new email:
[hidden email]
-----Original Message-----
From: SPSSX(r) Discussion <
[hidden email]> On Behalf Of Bruce Weaver
Sent: Friday, February 26, 2021 8:45 PM
To:
[hidden email]
Subject: Re: GENLINMIXED EMMEANS don't agree with descriptives
Thanks for providing that example. I am not surprised that the EMMEANS do not match the MEANS, given that you are using a binomial error distribution and a logit link. If you change those to normal error distribution and identity link (as shown below), the EMMEANS do match the MEANS. (If this "risk difference" kind of model makes sense, you'll probably want to use the ROBUST covariance estimator too, as I have done below.)
VARIABLE LEVEL CHOICE (SCALE).
GENLINMIXED /DATA_STRUCTURE SUBJECTS=SUB /FIELDS TARGET=CHOICE TRIALS=NONE OFFSET=NONE /TARGET_OPTIONS DISTRIBUTION=NORMAL LINK=IDENTITY REFERENCE=0 /FIXED EFFECTS= AC WT AC*WT USE_INTERCEPT=TRUE /RANDOM USE_INTERCEPT=TRUE SUBJECTS=SUB /EMMEANS TABLES=AC*WT /BUILD_OPTIONS TARGET_CATEGORY_ORDER=aSCENDING INPUTS_CATEGORY_ORDER=aSCENDING COVB = ROBUST.
MEANS CHOICE BY AC BY WT.
Beckstead, Jason-2 wrote
> Thanks Bruce. Below is small data and syntax.
>
>
> * Encoding: UTF-8.
> *-9 within-subjects conditions (3 x 3; AC x WT) & binary choice response.
> *-below is hypothetical data from N=6 subjects.
> *-At issue: estimated means do not agree with observed means.
> DATA LIST FREE /SUB AC WT CHOICE.
> BEGIN DATA.
> 1 1 1 0
> 1 1 2 0
> 1 1 3 0
> 1 2 1 0
> 1 2 2 1
> 1 2 3 1
> 1 3 1 1
> 1 3 2 1
> 1 3 3 1
> 2 1 1 0
> 2 1 2 0
> 2 1 3 1
> 2 2 1 0
> 2 2 2 0
> 2 2 3 1
> 2 3 1 0
> 2 3 2 1
> 2 3 3 1
> 3 1 1 0
> 3 1 2 1
> 3 1 3 0
> 3 2 1 1
> 3 2 2 1
> 3 2 3 0
> 3 3 1 1
> 3 3 2 1
> 3 3 3 0
> 4 1 1 0
> 4 1 2 0
> 4 1 3 0
> 4 2 1 1
> 4 2 2 1
> 4 2 3 1
> 4 3 1 1
> 4 3 2 1
> 4 3 3 1
> 5 1 1 0
> 5 1 2 0
> 5 1 3 0
> 5 2 1 0
> 5 2 2 0
> 5 2 3 0
> 5 3 1 0
> 5 3 2 0
> 5 3 3 0
> 6 1 1 1
> 6 1 2 1
> 6 1 3 1
> 6 2 1 1
> 6 2 2 1
> 6 2 3 1
> 6 3 1 1
> 6 3 2 1
> 6 3 3 1
> END DATA.
>
> VARIABLE LEVEL SUB AC WT (NOMINAL).
> 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
> /RANDOM USE_INTERCEPT=TRUE SUBJECTS=SUB /EMMEANS TABLES=AC*WT
> /BUILD_OPTIONS TARGET_CATEGORY_ORDER=aSCENDING
> INPUTS_CATEGORY_ORDER=aSCENDING.
>
> MEANS CHOICE BY AC BY WT.
-----
--
Bruce Weaver
[hidden email]
https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fsites.google.com%2Fa%2Flakeheadu.ca%2Fbweaver%2F&data=04%7C01%7Cjbeckste%40USF.EDU%7C878a650f35ca4810f58d08d8dac14b99%7C741bf7dee2e546df8d6782607df9deaa%7C0%7C0%7C637499871024726099%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=WbEFDlOLyruVkJ35luD4Db7txqhE%2BL%2FIuka9osK6PgI%3D&reserved=0"When all else fails, RTFM."
NOTE: My Hotmail account is not monitored regularly.
To send me an e-mail, please use the address shown above.
--
Sent from:
https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fspssx-discussion.1045642.n5.nabble.com%2F&data=04%7C01%7Cjbeckste%40USF.EDU%7C878a650f35ca4810f58d08d8dac14b99%7C741bf7dee2e546df8d6782607df9deaa%7C0%7C0%7C637499871024726099%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Cy9fTQlhxgHGTtp4aK16lJ%2FHlytq8mfX6mVj0pGuJtM%3D&reserved=0=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD [EXTERNAL EMAIL] DO NOT CLICK links or attachments unless you recognize the sender and know the content is safe.
=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD