Definition Let X : Random variable with pdf/pmf f(x;θ),θ∈Ω X′=(X1,…,Xn) : Random sample on X Consider Hypotheses H0:θ∈ω0 versus H1:θ∈ω1 A test with critical region C and significance level α If Pθ(X∈C)≥α,∀θ∈ω1 Then we say that this test is unbiased Related Neyman-Pearson Theorem