Page 1 Lecture 11: Attribute Charts Spanos EE290H F05 1 P-chart (fraction non-conforming) C-chart (number of defects) U-chart (non-conformities per unit) The rest of the “magnificent seven” Control Charts for Attributes Page 2 Lecture 11: Attribute Charts Spanos EE290H F05 1 P-chart (fraction non-conforming) C-chart (number of defects) U-chart (non-conformities per unit) The rest of the “magnificent seven” Control Charts for Attributes Lecture 11: Attribute Charts Spanos EE290H F05 2 Yield Control 30 20 10 0 0 20 40 60 80 100 Months of Production 30 20 10 0 0 20 40 60 80 100 Yield Page 3 Lecture 11: Attribute Charts Spanos EE290H F05 1 P-chart (fraction non-conforming) C-chart (number of defects) U-chart (non-conformities per unit) The rest of the “magnificent seven” Control Charts for Attributes Lecture 11: Attribute Charts Spanos EE290H F05 2 Yield Control 30 20 10 0 0 20 40 60 80 100 Months of Production 30 20 10 0 0 20 40 60 80 100 Yield Lecture 11: Attribute Charts Spanos EE290H F05 3 The fraction non-conforming The most inexpensive statistic is the yield of the production line. Yield is related to the ratio of defective vs. non-defective, conforming vs. non-conforming or functional vs. non- functional. We often measure: • Fraction non-conforming (P) • Number of defects on product (C) • Average number of non-conformities per unit area (U) Page 4 Lecture 11: Attribute Charts Spanos EE290H F05 1 P-chart (fraction non-conforming) C-chart (number of defects) U-chart (non-conformities per unit) The rest of the “magnificent seven” Control Charts for Attributes Lecture 11: Attribute Charts Spanos EE290H F05 2 Yield Control 30 20 10 0 0 20 40 60 80 100 Months of Production 30 20 10 0 0 20 40 60 80 100 Yield Lecture 11: Attribute Charts Spanos EE290H F05 3 The fraction non-conforming The most inexpensive statistic is the yield of the production line. Yield is related to the ratio of defective vs. non-defective, conforming vs. non-conforming or functional vs. non- functional. We often measure: • Fraction non-conforming (P) • Number of defects on product (C) • Average number of non-conformities per unit area (U) Lecture 11: Attribute Charts Spanos EE290H F05 4 The P-Chart P{D = X} = n x p x (1-p) n-x x = 0,1,...,n mean np variance np(1-p) thesamplefraction p= D n mean p variance p(1-p) n The P chart is based on the binomial distribution: Page 5 Lecture 11: Attribute Charts Spanos EE290H F05 1 P-chart (fraction non-conforming) C-chart (number of defects) U-chart (non-conformities per unit) The rest of the “magnificent seven” Control Charts for Attributes Lecture 11: Attribute Charts Spanos EE290H F05 2 Yield Control 30 20 10 0 0 20 40 60 80 100 Months of Production 30 20 10 0 0 20 40 60 80 100 Yield Lecture 11: Attribute Charts Spanos EE290H F05 3 The fraction non-conforming The most inexpensive statistic is the yield of the production line. Yield is related to the ratio of defective vs. non-defective, conforming vs. non-conforming or functional vs. non- functional. We often measure: • Fraction non-conforming (P) • Number of defects on product (C) • Average number of non-conformities per unit area (U) Lecture 11: Attribute Charts Spanos EE290H F05 4 The P-Chart P{D = X} = n x p x (1-p) n-x x = 0,1,...,n mean np variance np(1-p) thesamplefraction p= D n mean p variance p(1-p) n The P chart is based on the binomial distribution: Lecture 11: Attribute Charts Spanos EE290H F05 5 The P-chart (cont.) p= m S i=1 p i m mean p variance p(1-p) nm (in this and the following discussion, "n" is the number of samples in each group and "m" is the number of groups that we use in order to determine the control limits) (in this and the following discussion, "n" is the number of samples in each group and "m" is the number of groups that we use in order to determine the control limits) p must be estimated. Limits are set at +/- 3 sigma.Read More

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