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# Error - Control Chart Methods for Individual Measurements...

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Control Chart Methods for Individual Measurements IE 330: Lecture 9 2/11/2008

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Outline Why not sample more? Shewart type charts Example: White millbase dispersion process Exponentially weighted moving average control charts
Why not sample more? (n=1)

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X and R m Control Charts Idea: Calculate the range from consecutive individual measurements: usually n=2 or 3 R A x ULC x CL R A x LCL 2 2 + = = - = X i = 12 15 13 12 14 18 13 R1=3 R2=3 R3=1 R4=6
n should be small: Special causes might be present Most misused: Only use if samples cannot be formed. 1. Higher variability 2. Large sampling errors X and R m Control Charts

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Construction of Control Charts Center line
Construction of Control Charts m m m R D R R D 4 3 UCL CL LCL = = =

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Construction of Control Charts ) ( ˆ 2 n d R m = σ m R R m d R mn x m x X m i i m i k j ij m i i x ∑∑ = = = = = = = = = 1 2 1 1 1 ; ) ( ˆ ; ˆ σ μ R A x k d R x k x x x 2 2 / 3 ˆ 3 ˆ 3 ˆ ± ± ± ± σ σ μ σ ˆ 3 ± X Estimate variance UCL and LCL
Example: White Millbase

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