STATISTICAL SAMPLING

Since the cancellation MIL-STD-105E, the availability of statistically sound, sampling tables to personnel performing in-process and end item product audits has been scarce. Most people performing these audits today, are still using tables from this canceled document or are using Contractor's Sampling Tables.  The table below is approved for use by DCMA QA personnel performing zero-based sampling.   If no AQL is contractually specified, an AQL of 1.0% is suggested.  

  ZERO-BASED ACCEPTANCE SAMPLING PLAN
"A Indicates that the Entire Lot Must be Inspected"

        Acceptable Quality Level (AQL)
LOT SIZE .010% .015% .025% .040% .065% .10% .15% .25% .40% .65% 1.0% 1.5% 2.5% 4.0% 6.5% 10.0%
1-8 A A A A A A A A A A A A 5 3 2 2
9-15 A A A A A A A A A A 13 8 5 3 2 2
16-25 A A A A A A A A A 20 13 5 3 3 2
26-50 A A A A A A A A 32 20 13 8 5 5 5 2
51-90 A A A A A A 80 50 32 20 13 8 7 6 5 4
91-150 A A A A A 125 80 50 32 20 13 12 11 7 6 5
151-280 A A A A 200 125 80 50 32 20 20 19 13 10 7 6
281-500 A A A 315 200 125 80 50 48 47 29 21 16 11 9 7
501-1200 A 800 500 315 200 125 80 75 73 47 34 27 19 15 11 8
1201-3200 1250 800 500 315 200 125 120 116 73 53 42 35 23 18 13 9
3201-10,000 1250 800 500 315 200 192 189 116 86 68 50 38 29 22 15 9
10,001-35,000 1250 800 500 315 300 294 189 135 108 77 60 46 35 29 15 9
35,001-150,000 1250 800 500 490 476 294 218 170 123 96 74 56 40 29 15 9
150,001-500,000 1250 800 750 715 476 345 270 200 156 119 90 64 40 29 15 9
500,001 & Over 1250 1200 1112 715 556 435 303 244 189 143 102 64 40 29 15 9

Other Available Sources - There are some documents that are currently available that can be used that contain certified statistically sound sampling tables. 

1. ZERO ACCEPTANCE NUMBER SAMPLING PLANS fourth edition by Nicholas L. Squeglia. This book gives a number of zero based sampling plans and their corresponding Operating Characteristic (OC) Curves and Values. It is the state of the art in zero based sampling plans. It's only draw back is as with all zero based sampling plans, the OC curves flatten out at the bottom. This means when the probability of you accepting a bad lot goes down to approximately 10% or below, you would be more apt to accept a bad lot using a zero based sampling plan. This document is made available by ASQC, Quality Press, 611 East Wisconsin Avenue, Milwaukee, Wisconsin 53202.

2. MIL-STD-1916, DoD PREFERRED SAMPLING PLANS FOR ACCEPTANCE OF PRODUCT This document contains a set of statistically sound sampling plans and procedures for planning and conducting the inspection of product to assess quality and provide information of conformance to contract requirements. This new military standard complies with the Department of Defense policy of eliminating acceptable quality levels (AQLs) and associated practices. The standard is currently available, however, the handbook addressing this standard and providing clarification is still being written. Also, some of these plan may be too stringent to use, based on contract requirements.

3. Electronic Industries Association (EIA) Standard, ZERO ACCEPTANCE NUMBER SAMPLING PROCEDURES AND TABLES FOR INSPECTION BY ATTRIBUTES BY A CONTINUOUS MANUFACTURING PROCESS Since conventional attribute sampling plans based on nonzero acceptance are no longer desirable, this industry standard places an emphasis on zero based sampling plans as they relate to Lot Tolerance Percent Defective (LTPD) value or the limiting quality protection of MIL-STD-105. The OC curves of this document are for the most part equal to or better than their associated MIL-STD-105 curves. Published by Electronic Industries Association, Engineering Department, 2001 Pennsylvania Ave. N.W., Washington, D.C. 20006. EIA Standard Sales Dept (202/457-4966).

You may wish to note if you still have contracts which require MIL-STD-105, American Society for Quality Control, now has available, ASQC Z1.4. a virtual exact copy of MIL-STD-105E.

Remember also, that in order to use the Contractor's sampling plan, the plan shall afford us equal or better protection that the requirements of the contract.