Figure 5

AIC model densities versus AIC model rank. A) and C) show models that had non-singular Hessians (matrices of objective function second derivatives) at their optimums; B) and D) are models with singular (determinant = 0) Hessians, i.e. models that converged onto likelihood surfaces that were flat in one direction. C) and D) show 1613 and 475 models with SSEs < twice the minimum SSE.