The well-known variance decomposition rule is given by:
V a r [ W ] = V a r [ E [ W | V ] ] + E [ V a r [ W | V ] ] {\displaystyle Var[W]=Var[E[W|V]]+E[Var[W|V]]}
![{\displaystyle Var[W]=Var[E[W|V]]+E[Var[W|V]]}](/media/api/rest_v1/media/math/render/svg/e392815aa49e3c35eda850050974ea71a7e890ec)
