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Quality & Reliability Engineering

Shewhart control charts for dispersion adjusted for parameter estimation

, , , , , & show all
Pages 838-848 | Received 16 Jun 2016, Accepted 10 Feb 2017, Published online: 24 May 2017

Figures & data

Figure 1. Boxplots of 1000 simulated values of in-control (γ = 1) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0.1, and p = 0.1. The dashed vertical line indicates CARLtol = 1/αtol = 182, and the p-quantiles are indicated with an added vertical line in the boxplots.

Figure 1. Boxplots of 1000 simulated values of in-control (γ = 1) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0.1, and p = 0.1. The dashed vertical line indicates CARLtol = 1/αtol = 182, and the p-quantiles are indicated with an added vertical line in the boxplots.

Figure 2. Boxplots of 1000 simulated values of out-of-control (γ = 1.5) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0.1 , and p = 0.1.

Figure 2. Boxplots of 1000 simulated values of out-of-control (γ = 1.5) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0.1 , and p = 0.1.

Figure 3. Boxplots of 1000 simulated values of in-control (γ = 1) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0, and p = 0.05. The dashed vertical line indicates CARLtol = 1/αtol = 200, and the p-quantiles are indicated with an added vertical line in the boxplots.

Figure 3. Boxplots of 1000 simulated values of in-control (γ = 1) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0, and p = 0.05. The dashed vertical line indicates CARLtol = 1/αtol = 200, and the p-quantiles are indicated with an added vertical line in the boxplots.

Figure 4. Boxplots of 1000 simulated values of out-of-control (γ = 1.5) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0 , and p = 0.05.

Figure 4. Boxplots of 1000 simulated values of out-of-control (γ = 1.5) CARL. Parameter values are m = 50, n = 5, α = 0.005, ϵ = 0 , and p = 0.05.

Table 1. Required values of a and b (and a0 and b0) for different estimators used in the calculation of the adjusted control limit.

Table 2. Control limit coefficients: Unadjusted and adjusted for Sp with ϵ = 0.10 (α = 0.005). Every second row (in italics) gives the ratio between the adjusted and the unadjusted limit.

Table 3. Control limit coefficients: Unadjusted and adjusted for Sp with ϵ = 0.20 (α = 0.005). Every second row (in italics) gives the ratio between the adjusted and the unadjusted limit.

Table 4. Out-of-control CARL for γ = 1.5 of the S chart with and without the adjusted limits, when W = 1 (α = 0.005).

Table 5. Out–of-control CARL for γ = 2.0 of the S chart without and with adjusted limits, when W = 1 (α = 0.005).

Figure 5. Application of the proposed control chart to the piston ring data set. Both the unadjusted and adjusted control limits are indicated.

Figure 5. Application of the proposed control chart to the piston ring data set. Both the unadjusted and adjusted control limits are indicated.