Sample Size

Manufacturing, inspection, exclusions


If we have a lot size of 27 and we are using a normal inspection level II with an AQL of 2.5. What is the sample size?


Assuming an attribute is being measured, we use ANSI ASQ Z1.4.2013 to find the sample size.

Given a lot size of 27 we first find in Table I. Sample Size Code Letter that Code letter D represents the sampling plan code letter for lot sizes between 26 and 50 for normal sampling (General Inspection Level II).

The move to Table II-A Single sampling plans for normal inspection to find the row for code letter D and under column for ASQ 2.5 find an up arrow. This indicates that we should use the code letter C which suggests a sampling plan of 5 samples and accept the lot if there are zero defect and reject the lot with one or more rejects.

Hope that helps.



Fred Schenkelberg
Reliability Engineering and Management Consultant
FMS Reliability
(408) 710-8248

For more on this topic, please visit ASQ’s website.

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