X̄ chart with R: 3/(d₂√n)
X̄ chart with S: 3/(c₄√n)
S chart lower: max(0, 1 − 3√(1−c₄²)/c₄)
S chart upper
E[s]/σ
E[R]/σ
√Var(R/σ)
R chart lower: max(0, 1 − 3 d₃/d₂)
R chart upper
X̄ chart with R: 3/(d₂√n)