proposition: Lemma variance_ge0 (X : {RV P >-> R}) : (0 <= 'V_P[X])%E.
proof: Proof. by rewrite /variance unlock; apply: expectation_ge0 => x; apply: sqr_ge0. Qed.
imports: mathcomp(all_ssreflect) mathcomp(ssralg poly ssrnum ssrint interval finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality) HB(structures) exp numfun lebesgue_measure lebesgue_integral reals ereal signed topology normedtype sequences esum measure exp numfun lebesgue_measure lebesgue_integral