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Four quantities are needed for
the calculation of sample size:
3.
The contamination rate that is considered
unacceptable. The level at which one
would want to take action. This is called
the Rejectable Quality Level (RQL).
4.
The error rate for not acting when the lot
is at the RQL. This is the Type 2 error or
Consumer’s risk. A typical Type 2 error
is 10%.
But AQL and RQL are currently 0 and 1
Statistical confidence based on
sample numbers
•
Using Type 1 error rate of 5% and a Type 2
e o ate of 10% ith 60 samples the
rr r r
, w
,
“AQL” is 0.09% and the “RQL” is 3.8% (for
a sampling plan that accepts with no
positives and rejects with 1 positive)
•
If 0.09% of the individual samples are
contaminated, 5% of the time the lot would
be rejected. If 3.8% of the individual
samples are contaminated, 10% of the
time the lot would be accepted