What about the sampling rule based on the "square root of (N) + 1"?
What are its origins?
Is this a valid sample size formula?
The article "The Square Root of N Plus One Sampling Rule.pdf" (attached below) by Pharmtech gives a good overview of the origins of this sampling rule, along with reviews of the assessment of its validity.
[Quality Focus article] "When is a sample not a sample.pdf" (attached below)
Article "WHO Pharmaceutical Technical Report Series 929.pdf" (see page 85 of 152) (attached below).
Pharmtech article "Statistical Solutions -- Square Root of (N) Plus One Sampling Plan.pdf" (attached below).
Scanned article excerpt "Square Root N Plus One -- attributed to Dodge.pdf" (attached) attributes the sampling plan to Harold Dodge.
Other related information:
In general, I believe that there is enough question about its validity (or at least the circumstances under which it might be valid) that I would not advocate its use; particularly if other, more statistically valid and generally accepted methods are available.