{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lec 12 - Attributes Control Charts

# Lec 12 - Attributes Control Charts - Attributes Control...

This preview shows pages 1–8. Sign up to view the full content.

Attributes Control Charts Variables Control Charts for continuous measurements Attribute Control Charts for discrete measurements

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
P Charts for Fraction Defective Monitors fraction defective Defective is unusable fraction of broken glass plates fraction of defective chips on a wafer fraction of defective truffle shells go-no-go gauge 2
P Chart Based on Binomial Distribution sample size n for sample i X i = number of defectives in sample of n p = fraction defective in pop’ln = P(unit is defective) r.v. X Binomial(n, p) P(X x = 0,1, ... , n i i = = - - x n x p p x n x ) ( ) 1 E(X)=np V(X)=np(1-p) 3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Sample Statistic is Fraction Defective At each sample time plot p x n i i = Note: E p n E x p V p n V x np p n p p n i i i i ( ) ( ) ( ) ( ) ( ) ( ) = = = = - = - 1 1 1 1 2 2 Control Limits UCL p p p n LCL p p p n = + - = - - 3 1 3 1 ( ) ( ) CL = p 4
Some Notes on P Charts If LCL is negative, make it zero Test statistic is not normal - don't use zone rules If p i = 0, process in-control 5

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Estimating p From Initial Data Data: draw m (say 20) subsamples of size n X 1, X 2 , ... , X m Sample Statistics: p 1, p 2 , ... , p m Estimate for CL = p p x x nm m = + + 1 ... 6
Example for P Charts A process that produces bearing housings is investigated. 10 samples of size 100 are selected. Is process in-control?

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 21

Lec 12 - Attributes Control Charts - Attributes Control...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online