Switching Rules


Question 

We are planning to implement ANSI/ASQ Z1.4-2003(R2013) sampling inspection plan with our Finish products which are currently 100% inspected by QC Inspectors.  I read  about the importance of the switching rules  on a continuing stream of lots and have the following  questions:
1.Is it acceptable to select a specific plan (tightened, normal or reduced ) and use it without the switching rules?
2.Are there any exceptions which allow us to use a specific plan without applying  the switching rules?

Answer

  1. You can use any plan without using the switching rules but it does run the risk of not meeting the alpha risk in the end. These plans were developed to be used as documented. A normal plan is generally used and the switching rules come in when the clearance number has been obtained.  Some processes may never switch.  If you choose a plan that is tightened or reduced to start with, you potentially will either spend too much on inspection (tightened) or risk having bad product go to the customer (reduced).  It is a business decision for you to make if your customer is not demanding it.  The switching rules are there to protect the producer when the product is running very well or it has problems.
  2. If your customer is not requiring a particular plan, you can use what you want. It is a business decision, no reason for any exceptions.

I hope this helps.

Jim Bossert
Sr Performance Improvement Specialist
JPS Hospital
ASQ Fellow, CQE, CQA, CMQ/OE, CSSBB, CSSMBB
Fort Worth, TX

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