inverseHessian
a character string specifying the way of inverting the Hessian matrix.
It takes values in “overall” and “block”. The choice depends on whether the intercepts $\mu_M$ and $\mu_P$
should be treated disjointedly from other parameters.
inverseHessian=“overall” inverts the whole Hessian matrix directly.
inverseHessian=“block” chooses to invert two diagonal blocks of the Hessian matrix (a block corresponding to intercept parameters, and a block corresponding to non-intercept parameters),
and combines the invidual inverse.