Six Sigma

Note that chart “designer” or user could use the ARL formula to decide which sample size to use. For example, if it is important to detect 1σ0 process mean shifts within two periods with high probability such that ARL(Δ = 1σ0) < 2.0, then sample sizes equal to or greater than 10 should be used. Note also that ARL does not depend on the true mean, μ.