> Could you describe a little bit more about these 3 variables and explain why you consider them as random-effects variables? If you treat them as random-effects variables, they should not be included in the model specification because that is for fixed-effects variables:

1. Gotcha. So just to be clear, ranEff "~1" will estimate random intercepts for any variables specified in the dataTable that are NOT in the model?
2. Site, family ID and sibling are nested (and not crossed) random effects. The data were collected at multiple sites and contains siblings (i.e., family_ID) and twins/triplets (i.e., sib). There are different numbers of subjects and siblings/twins per site. Therefore, we want to include these factors as nested random effects.


> Do you mean that 'Age' varies within subject? Is this a longitudinal study? If so, yes you can do: -ranEff "~1+age" \

1. Yes, age varies within subject
2. Yes, this is a longitudinal study which means that the interval of the variation is different between subjects. For example, sub 1 is scanned at 14.2 yo and then again at 19.9 = 5.7 years vs sub 2 scanned at 14.9 and 19.0 = 4.1 years


To sum it up, would this be the correct way to model random effects for site, family_ID, sib plus the random slope for age?:

3dLME -prefix filename -jobs 12 \
-model "group*time*age+age+sex+handedness+IQ_PR+IQ_VC" \
-qVars "age,sex,handedness,IQ_PR,IQ_VC" \
-ranEff "~1+age" \
-SS_type 3 \
-dataTable \
Subj group age time sex handedness IQ_PR IQ_VC site family_ID sib InputFile \