[R-meta] including uninformative levels

Hello,

I hope you are well.
Is there any benefit/disadvantage of including levels in your model that
only have information coming from a single study? I always remove the
intercept and do not include it in the follow-up comparisons between levels
but wonder if there's a consequence to doing it this way since this one
study will potentially introduce more heterogeneity and does not add much
empirical value for this particular analysis.

Best wishes,

Catia

Dear C?tia

In general, in regression, if you have a level in one of the factors
which is represented by a single observation then that observation will
be perfectly fitted and that observation will have high leverage.

In a random-effects model since it should contribute to the between
study variation then it would affect all the estimates since the weights
are dependent on the estimate of tau^2.

Michael

On 03/12/2021 13:29, C?tia Ferreira De Oliveira wrote:

Hello,

I hope you are well.
Is there any benefit/disadvantage of including levels in your model that
only have information coming from a single study? I always remove the
intercept and do not include it in the follow-up comparisons between

levels

but wonder if there's a consequence to doing it this way since this one
study will potentially introduce more heterogeneity and does not add much
empirical value for this particular analysis.

Best wishes,

Catia

--
Michael
http://www.dewey.myzen.co.uk/home.html