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ASQ/ANSI Quality Control Standards: Z1.4 & Z1.9
The Z1.4 Standard
ANSI/ASQ Z1.4-2003 (R2013): Sampling Procedures and Tables for Inspection by Attributes is an acceptance sampling system to be used with switching rules on a continuing stream of lots for Acceptance Quality Limit (AQL) specified. It provides tightened, normal, and reduced plans to be applied for attributes inspection for percent nonconforming or nonconformities per 100 units.
The Z1.9 Standard
ANSI/ASQ Z1.9-2003 (R2013): Sampling Procedures and Tables for Inspection by Variables for Percent Nonconforming is an acceptance sampling system to be used on a continuing stream of lots for Acceptance Quality Limit (AQL) specified. It provides tightened, normal, and reduced plans to be used on measurements which are normally distributed. Variation may be measured by sample standard deviation, sample range, or known standard deviation. It is applicable only when the normality of the measurements is assured.
History of Z1.4 & Z1.9
Read an overview describing the origins and purposes of the statistical standards ANSI/ASQ Z1.4, which establishes sampling plans and procedures for inspection by attributes, and ANSI/ASQ Z1.9, which establishes sampling plans and procedures for inspection by variables.
Questions About Z1.4 and Z1.9? Ask the Experts!
Visit the Ask the Experts blog for help with your questions about the Z1.4 and Z1.9 standards.
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- “Comparing Acceptance Sampling Standards, Part I,” Quality Engineering, January 2013
- “Comparing Acceptance Sampling Standards, Part II,” Quality Engineering, April 2013
- ”Caveats Regarding the Use of Statistical Analysis” (members only), World Conference on Quality and Improvement, May 2009
- ”Attribute Acceptance Sampling as a Tool for Verifying Requirements Using Monte Carlo Simulation” (members only), Quality Engineering, April 2009
- ”A Sampling Plan for Contact Auditing in Call Centers” (members only), World Conference on Quality and Improvement, May 2010
- ”Evaluating and Implementing 3-Level Control Charts,” Quality Engineering, July 2006