jamovi

I have a question about covariance structure used by default in GAMLj Mixed Model. On the website: https://gamlj.github.io/mixed.html I found information that if we want to obtain a variance component (VC) model we should select "Not correlated" option in "Effects correlations" . Do I undestand correctly that by default this modul assumes unstructured covariance structure (UN) ?

Thanks a lot for all your help!
Asia

Yes, you assume well. GAMLj uses the same default that the underlying R lmer() command. Thus, UNstructured by default, meaning all random coefficients are allowed to be correlated.

I am a relative newbie to Mixed Models, with this perhaps naive question... If I use the Random Intercept Model then setting covariance structure (i.e. correlated or uncorrelated) does not matter, doesn't it? As the covariance is assumed for random components (i.e., more than one). While in the case of Random Intercept Model there is only one component, which is cluster variable?

Correct.
however, the one component is not the cluster variable but it is the intercept.