“…Quite often only the conditional mean function E(y|ξ) = m * (ξ, β), the regression in the narrower sense, is given, supplemented by a conditional variance function V(y|ξ) = v * (ξ, β, ϕ), where θ comprises β and ϕ plus possibly other parameters describing the distribution of y. Two major examples, that we will often refer to, are the polynomial model (for a survey see Cheng and Schneeweiss, 2002),…”