For a linear combination ∑ uj Xj of random variables, we are interested in the partial derivatives of its α-quantile Qα(u) regarded as a function of the weight vector u = (uj). It turns out that under suitable conditions on the joint distribution of (Xj) the derivatives exist and coincide with the conditional expectations of the Xi given that ∑ uj Xj takes the value Qα(u). Moreover, using this ...

In this paper we propose a new procedure for testing independence of random variables, which is based on the conditional expectation. As it is well known, the behaviour of the conditional expectation may determine a necessary condition for stochastic independence, that is, the so called mean independence. We provide a necessary and sufficient condition for independence in terms of conditional e...