Behavioral Genetics Models
Moritz
Joined: 02/10/2015
High MZ correlations exceed the Chronbach's alpha of the Questionnaire
Hi Everyone,
I have a more general question about MZ and DZ correlations and their relationship with the Chronbach's alpha of the questionnaire that is used.
I am running different twin models to estimates A,C and E contribution to variation in behaviours using a parent measured questionnaire in a sample of infants and toddlers.
When running the analyses I am consistently finding large MZ correlations (0.80-0.95) for the different traits, which exceed the chronbach's alpas of the scale.
James Sherlock
Joined: 06/03/2014
Multivariate Covariance Estimate CI's
I'm currently runnning a three variable Cholesky ACE model and am able to grab CI's for my variance estimates and correlations but my model crashes and gives me an NLOPT fatal error -1 when I attempt to retrieve confidence intervals for covariance estimates. I'm wondering if anyone can tell me why and how to retrieve the problematic CI's. Here's my script:
# -----------------------------------------------------------------------------------------------------------
# Script: 2ACE_Chol.R
# Fits a MV Cholesky ACE Decomposition
# Data File: Covariate Regressed Cross-trait Data.csv
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YiTan
Joined: 10/08/2014
ADE and submodels
Hi all,
I noticed in the ADE code (http://www.vipbg.vcu.edu/HGEN619_2014/twinAdeCon.R) that the only submodels considered are AE and E models. I would like to ask: why isn't the DE model a possible model to consider?
Thanks and best regards,
Yi Ting
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YiTan
Joined: 10/08/2014
Univariate Heterogeneity model with covariates (including DZO)
Hi all,
I tried to modify the heterogeneity model for MZM, DZM, MZF, DZF and DZO groups to include covariates. I got the following error message when I tried to run my code:
Running QualACE
Error: Unknown reference 'expMeanGf' detected in the entity 'expMeanGfm' in model 'DZo'
May I know what changes should I make to my code to run it successfully? My code is as follows:
require(OpenMx)
require(psych)
# ------------------------------------------------------------------------------
# PREPARE DATA
# Select Variables for Analysis
YiTan
Joined: 10/08/2014
Missing CIs - How to get them?
Hi all,
When I ran the univariate or bivariate scripts for some of my variables, I often get NA for some of the CIs requested, followed by this line: "Investigate missing CIs with the detail output in MxComputeConfidenceInterval "
I would like to know what causes the missing CIs and what can I do to get the missing CIs? I'm not sure if I understand what arguments to put in the MxComputeConfidenceInterval.
Thank you very much for the help!
Best Regards,
Yi Ting
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Inga
Joined: 09/02/2015
Using FIML to impute missing covariate data
I am running a simple ACE model with covariates (e.g., sex, age). Now I am trying to impute missing covariate data using full information maximum likelihood (FILM) (as described here: http://openmx.psyc.virginia.edu/docs/OpenMx/2.0.0-3838/FIML_RowFit.html).
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YiTan
Joined: 10/08/2014
On dealing with non-normality: transform the raw variables or the residuals?
Hi,
I would like to ask if I have considerably positively skewed raw data for my task performance measures, should I: 1) adjust the variables for covariates (e.g. age, sex and years of training) first, and then transform the residuals using maybe box-cox transformation; or 2) transform the raw variables before adjusting for the covariates?
I've initially done (2) but then I noticed in this paper (http://www.ncbi.nlm.nih.gov/pubmed/21336711) that transformation was done on the residuals, which seems to make more sense.
YiTan
Joined: 10/08/2014
Adjusting for effects of age and sex in sex-limitation models
Hi,
I would like to ask is it actually necessary to adjust for sex effects in sex-limitation models? or just adjusting for age would do?
Thanks!
-Yi Ting
Cindy.s
Joined: 07/04/2015
Normalize data?
Hi OpenMX community!
I have a probably strait forward question. I'm running simple Univariate ACE models with covariates. My dependent variable has non-normal distribution. Should I normalize my data, for example using the R function scale? Should I normalize my covariates also? My estimates only change slightly, my Chi-square values are basically the same, but my CFI and TLI values change a little bit, should this be of concern?
Thanks for your help!
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britt01
Joined: 08/04/2015
ACE Univariate Homogeneity vs OpenMx Tutorial
Hello,
First a thank you to this great forum! I am a beginner at twin model and have found it very helpful. I recently ran the Univariate Sex Limitation Model script http://www.vipbg.vcu.edu/HGEN619_2014/twinHet5AceCon.R At the end one runs a Homogeneity ACE model. My understanding is this should produce the same results as running the OpenMx ACE tutorial limited to just the young twins from the psych package, and excluding the opposite sex pairs. http://openmx.psyc.virginia.edu/docs/openmx/latest/GeneticEpi_Matrix.html