Zero Acceptance Sampling
  • CODE : WILE-0036
  • Duration : 60 Minutes
  • Level : Intermediate
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William A. Levinson, P.E., FASQ, CFPIM is the principal of Levinson Productivity Systems, P.C. and the author of several books on quality, productivity, and management.

This webinar will show how to convert any ANSI/ASQ Z1.4 (MIL-STD 105) sampling plan into a zero acceptance plan that offers comparable protection to the customer for far less work.

  • Know how ANSI/ASQ Z1.4 sampling plans work. This is a prerequisite for the use of zero acceptance sampling plans.
  • Know the benefits of double and multiple ANSI/ASQ Z1.4 sampling plans for lower (on average) inspection.
  • Convert any ANSI/ASQ Z1.4 plan into a zero acceptance number plan, and demonstrate to the customer that it offers comparable protection.
  • Recognize that the chief drawback of the zero acceptance plan is its propensity to reject good lots that would be accepted by the ANSI/ASQ Z1.4 plan, and be aware of alternatives like sequential sampling and narrow limit gauging that can be used if this is an issue.

Areas Covered  

  • Overview of ANSI/ASQ Z1.4 (formerly MIL-STD 105) including how to define a plan based on (1) the lot size, (2) the inspection level and (3) the acceptable quality level (AQL) at which we want to accept most (nominally 95%) of all lots.
  • The operating characteristic (OC) curve reflects the probability of acceptance versus the nonconforming fraction of the work.
  • Any ANSI/ASQ Z1.4 plan can be converted into a zero acceptance number plan that provides equivalent protection at the rejectable quality level (RQL). While ANSI/ASQ Z1.4 plans do not have formal RQLs, we pretend for analytical purposes that this is the nonconforming fraction at which the inspection plan will reject 90% of the lots. This RQL is also used for sequential sampling plans.
     - The zero acceptance number plan has the lowest average sample number (ASN) compared to ANSI/ASQ Z1.4 single, double, multiple sampling plans, and even sequential sampling plans.
     - The operating characteristic curve shows that the zero acceptance plan has a greater chance of rejecting lots for nonconforming fractions up to the RQL, assuring the customer that it is getting better protection than the original plan. This also shows that the chance of rejecting work at the AQL is far higher than the nominal 5%, which means the producer must be very confident in the quality level to use a zero acceptance number plan.
     - Another prerequisite for a zero acceptance number plan is a decision (with the customer) as to whether ANSI/ASQ Z1.4's switching rules must be used. If there is a significant chance of rejecting good lots, the switching rules will put the producer into tightened inspection very quickly.
     -  When zero acceptance number plans cannot be used, e.g., because quality is not good enough to avoid rejection of good lots, alternatives are available.
      1. ANSI/ASQ Z1.4 double and multiple sampling plans
      2. Sequential sampling plans require somewhat less inspection than multiple sampling plans.
      3. Narrow limit gauging offers enormous reductions in inspection, but requires (1) that the quality characteristic be normally distributed, (2) the quality characteristic can be checked with go/no-go gages that can be set to specific dimensions, and (3) increases in the nonconforming fraction are due solely to changes in the process mean.

Recommended reference: Squeglia, Nicholas L. Zero Acceptance Number Sampling Plans, current edition

Attendees will receive a handout of the presentation slides and notes, along with a spreadsheet that assists conversion of ANSI/ASQ Z1.4 plans into zero acceptance sampling plans.

Who Should Attend

Quality Managers, Engineers, Technicians, and others with responsibility for acceptance sampling activities.

Why Should You Attend 

Inspection is a mandatory but non-value-adding activity, so the less we can do (and still meet customer requirements), the better. Zero acceptance sampling, in which discovering even one nonconforming unit results in rejection of the lot, minimizes the necessary inspection at the cost of increasing the chance of rejecting good lots. If quality is excellent, however, the latter consideration can be ignored to reduce enormously the cost of inspection.

  • $199.00



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