If the observations xi are independent random variables with variance σ2 then according to the EWMA charts, the variance of zi will be ________________

• A. \(\sigma_{zi}^2 = \sigma^2 (\frac{λ}{2-λ})[1+(1+λ)^{2i}]\)
• B. \(\sigma_{zi}^2 = \sigma^2 (\frac{λ}{2-λ})[1+(1-λ)^{2i}]\)
• C. \(\sigma_{zi}^2 = \sigma^2 (\frac{λ}{2-λ})[1-(1-λ)^{2i}]\)
• D. \(\sigma_{zi}^2 = \sigma^2 (\frac{λ}{2+λ})[1-(1-λ)^{2i}]\)