. Theorem 12.3.1 (Results and derivations have already been discussed ) i.i.d X,,...,X, : N(4,o' ) uunknown, o' known; HE (-00;00) Let Zo =- X - H . o/ Vn pivotal if X - N(/.,0?) ), then 1. H : USH, VS. H : 1>U. => a size o critical region C = {x: z. >z_ } and *() =$|-Z- % o / Vn => a size o critical region C = {x :z.