Hi all,
For what it is worth, unfortunately it requires a license, you can
obtain negative estimates of variance parameters in asreml-R. I agree
with Thierry that negative estimates of variances are odd, but I have
seen at least one case where they were practical: to identify that
observations within a grouping level were actually very dissimilar while
there was almost no variation across grouping level averages. That
result was contrary to my expectation given the experimental design and
I may have missed it otherwise. Arguably my models were misspecified,
but that odd result helped me understand the biology of my system and
specify more appropriate models later.
As for uncertainties of variances I usually go with Bayesian packages :
MCMCglmm, brms, rstan, rjags... (or, again, asreml-R).
Best regards,
*************************************
Timoth?e Bonnet, PhD
Charg? de recherche / Researcher
Centre d?Etudes Biologiques de Chiz?
UMR 7372 Universit? de la Rochelle-CNRS
405 route de Priss? la Charri?re
79360 Villiers en Bois
timotheebonnetc at gmail.com
https://timotheenivalis.github.io//