Variance of a treatment contrast
= Variance of a treatment contrast
{title2=$\operatorname{Var}(c^T\widehat\mu)=c^T\operatorname{Cov}(\widehat\mu)c$}
= Treatment-contrast variance
{synonym}
For a vector of estimated treatment means $\widehat\mu$, the <variance of a treatment contrast> with coefficient vector $c$ is $c^T\operatorname{Cov}(\widehat\mu)c$. Averaging subsamples from a common <experimental unit> does not make their shared <variance component> disappear.