Why || doesn't zero out the correlations in lmer
Thank you, this is extremely helpful to know. You mentioned it's well documented, any possible links to share? Also, does nlme::lme() behave in the same manner in this regard?
On Fri, Oct 8, 2021 at 4:46 PM Phillip Alday <me at phillipalday.com> wrote:
This is a well-documented issue: || doesn't zero correlations between a categorical variable's levels. As far as I know, there are software-development/technical reasons for this, not statistical ones. The afex package has an implementation that zeroes everything out. On 8/10/21 4:32 pm, Simon Harmel wrote:
Dear Colleagues,
I have a 'factor' predictor called 'type' (with 4 levels). In the
random part, I have used `||` so the levels of 'type' can't correlate
with each other.
But I wonder why still correlations are reported in the output?
Thanks, Simon
lmer(y~type + (type || ID), data = data)
Random effects:
Groups Name Std.Dev. Corr
ID type0 0.4276
type1 0.7012 0.81
type2 0.7115 0.72 0.97
type3 0.7655 0.83 1.00 0.98
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