Formally .Let Sm=X1+..+Xn,where the Xi are i.i.d.random variables with mean u,variance o2. 。Define Sn-nW_X1+…+Xn-nw Zn= 0√mFormally • Let 𝑆𝑛 = 𝑋1 + ⋯ + 𝑋𝑛, where the 𝑋𝑖 are i.i.d. random variables with mean 𝜇, variance 𝜎 2 . • Define 𝑍𝑛 = 𝑆𝑛 − 𝑛𝜇 𝜎 𝑛 = 𝑋1 + ⋯ + 𝑋𝑛 − 𝑛𝜇 𝜎 𝑛