st: model equation multilevel xtmixed

[Hanna Lomander <Hanna.Lomander@slu.se>]

Dear all,

We are doing a model with random intercept and random slope, as described in Rabe-Hesketh: Multilevel and longitudinal modeling using Stata. The data includes outcomes measured on cows within herds.

The model statement used is:  

xi: xtmixed glu i.group dim i.breed i.par i.season || farm: || id:dim, cov(unstructured) reml. 

We think that this how the model equation should be written, but since we are not used to this approach we are not sure:

Yijk = β1 + β2χijk +...+  ζ1i + ζ2jχijk + εijk
where Yijk  = the response of cow i in herd j at occasion k; β1 = the intercept;χijk =  the covariates for cow i in herd j at occasion k; ( We have 3 or 4 more covariates)ζ1j= the random intercept of cow i; ζ2jχijk; = the random slope of cow i in herd j at occasion k; εijk= a random term of cow i in herd j at occasion k.
What would you think, does this look right to you?  We would be extremely happy for some input!

Best regards,
Hanna


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