ANSI/ASQ Z1.9 (formerly MIL STD 414) uses sample statistics to determine whether a production lot, or incoming lot, should be accepted or rejected. These statistics also allow estimation of the nonconforming fraction at each specification limit. Attendees will learn how to define a sample plan on the basis of (1) the lot size, (2) the inspection level, and (3) the acceptable quality limit (AQL).
ANSI/ASQ Z1.9 can be used for single specification limits, two-sided specification limits, and even two-sided limits with different AQLs. Attendees will learn everything they need to know to address all three of these applications.
Switching rules meanwhile dictate normal, tightened, or reduced inspection according to production performance. Poor quality results in tightened inspection, while a consistent history of good quality and consistent production conditions allows reduced inspection. In addition, if the process is under control and its standard deviation is known, a considerably smaller sample size is required.
ANSI/ASQ Z1.9 is a widely recognized and generally accepted standard for acceptance sampling by variables. It uses the average and standard deviation (or range) of a sample of n parts to determine whether the lot from which the sample was drawn should be accepted or rejected. The technology is very straightforward, but users must also be aware of the often-overlooked fact that the standard relies on the assumption that the part measurements follow the normal or bell curve distribution. If this is not the case, the standard will not deliver the intended or expected results.
Attendees will also learn pitfalls that are involved in use of the sampling tables, and also use of the range method. It is important to remember that this approach uses the average range of samples of 5, rather than the range of (for example) all 15 parts in the sample.
Handouts will include a technical appendix that shows the derivation of some of the material in the standard such as operating characteristic (OC) curves, and an Excel spreadsheet that duplicates tables B5 and D5, which return estimates of the nonconforming fraction in the lot when the standard deviation is estimated from the sample statistics (B5) or known from prior experience (D5).
This webinar will equip attendees to understand and apply the ANSI/ASQ Z1.9 (formerly MIL STD 414) standard for acceptance sampling by variables (real number data), along with vital considerations such as the need to test the measurements for conformance to the normal (bell curve) distribution.
Quality engineers, technicians, and inspectors who use ANSI/ASQ Z1.9 (formerly MIL-STD 414)
William Levinson is the principal of Levinson Productivity Systems, P.C. He is an ASQ Fellow, Certified Quality Engineer, Quality Auditor, Quality Manager, Reliability Engineer, and Six Sigma Black Belt. He holds degrees in chemistry and chemical engineering from Penn State and Cornell Universities, and night school degrees in business administration and applied statistics from Union College, and he has given presentations at the ASQ World Conference, ISO/Lean Six Sigma World Conference, and others.View all trainings by this speaker