What is the value of lower cusum in the standardized scale cusum chart for process variability?

\(S_i^+=max⁡\left\{0,-v_i-k+S_{i-1}^+\right\}\)

\(S_i^+=max⁡\left\{0,v_i-k+S_{i-1}^+\right\}\)

\(S_i^-=max⁡\left\{0,v_i-k+S_{i-1}^+\right\}\)

\(S_i^-=max⁡\left\{0,-v_i-k+S_{i-1}^-\right\}\)

\(S_i^+=max⁡\left\{0,-v_i-k+S_{i-1}^+\right\}\)

What is the value of lower cusum in the standardized scale cusum char

1.	What is the value of lower cusum in the standardized scale cusum chart for process variability?
A.	\(S_i^+=max⁡\left\{0,v_i-k+S_{i-1}^+\right\}\)
B.	\(S_i^-=max⁡\left\{0,v_i-k+S_{i-1}^+\right\}\)
C.	\(S_i^-=max⁡\left\{0,-v_i-k+S_{i-1}^-\right\}\)
D.	\(S_i^+=max⁡\left\{0,-v_i-k+S_{i-1}^+\right\}\)
Answer» D. \(S_i^+=max⁡\left\{0,-v_i-k+S_{i-1}^+\right\}\)