random effects models with small n
Not knowing more about the data, I have to guess that multiple measurements were taken on each of the 16 animals, making the sample size larger than 16. http://en.wikipedia.org/wiki/Statistical_unit Tom
On Fri, Jun 17, 2011 at 7:08 AM, Felix Bach <Felix_Bach at gmx.de> wrote:
Dear all, I recently saw an article in which the authorsperformed a random effects analysis with lme4 ?which used a group (2 levels)x condition (3 levels) x effect (4 levels) and ratio (10 levels) as fixed factors and subject as random factor. Sample size was 16 animals. They used MCMC estimation and obtained p-values of 0.0001 (lets ignore the use of p values in a Bayesian framework). How reliable are those estimates? I can't imagine that you can reliable are p-values (or credibility intervals) with such a complex models and a sample size of 16? If the model assumption of an exchangable covariance structure is valid, could you trust the results? Best wishes, Felix --
_______________________________________________ R-sig-mixed-models at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models