Where the \(\sigma^{2}\) variances were obtained as the reciprocal of
the precisions (\(\tau\)) mentioned in the model description.
All the models were fitted using rjags, an R (---R Core Team 2016---)
interface to JAGS (Just Another Gibbs Sampler, \cite{Plummer2015}) which
uses Gibbs Sampling to estimate the marginal posterior distributions for
the parameters of interest. Approximately 35% of the strain data was
left-censored, and missing values due to censoring were imputed by JAGS
as a random value below the limit of detection (using the function
dinterval; for details see \cite{Lunn2012}, but above -1.5
(equivalent to a negative strain of 1500 micro-strains). We used a
family model instead of an animal model as, for the purposes of a simple
one-generation pedigree the models are equivalent (sensu
identical expected values and variance, \cite{Henderson_1985}), while the
family model is much less computationally intensive. The R/JAGS code is
available as supplementary material.