Relative Convexity

which, for invertible φ can also be expressed as, EX ≤ φ−1(E φ(X)) The term φ−1 ( E φ(X) ) can be seen as a generalized mean value [2],[1, ch.3]. The Lp norms (E|X|p)1/p for example fit this framework. The notion of convexity was generalized by B. Jessen in [2] to compare two functions in terms of the means defined by them. An increasing function φ is defined to be convex with respect to another increasing function ψ if,