... ph´ep ¯d’ˆoi bi´ˆen ui=x0i− 8, 50, 5(x0= 8, 5; h = 0, 5)Ta c´o u = −1350= −0, 26. Suy rax = 8, 5 + 0, 5.(−0, 26) = 8, 37s2= (0, 5)2.9550− (−0, 26)2= 0, 4581 ∼ (0, ... m˜ˆau.i) Tr’u`’ong h’o.p bi´ˆet V ar(X) = σ2:T`’u cˆong th´’uc ε = u2γσ√nta suy ran = u2γσ2ε2ii) Tr’u`’ong h’o.p ch’ua bi´ˆet σ2:3. B`ai t.ˆap 81Do ... ¯dˆo.c’ua Xith`ıf(x, µ) =1σ√2πe−(x−µ)2/2σ2Ta c´o∂∂µlnf(x, µ) =x − µσ2. Suy ra nE∂lnf(x, µ)∂µ2= nEx − µσ22=nσ2. Do ¯d´o V ar(X) ch´ınh b`˘ang nghi.ch¯d’ao...