From: Stan Hilliard
Date: 01 Feb 2000
Time: 16:01:41
Greetings Jim,
The rule: "square root of n plus 1" is a simple way to estimate the number of cells to have in a histogram to observe the shape of the distribution.
However, if this rule is applied to sample size, there would be no single oc curve associated with it. The ability to discriminate between acceptable and rejectable quality levels would change with lot size. The consequence is that it is not possible to make a single statement that describes the protection offered by the rule. Discussion of using the oc curve is here:
www.samplingplans.com/usingoccurves.htm
The software programs TP105 and TP414 can generate oc curves for any n,Ac combination. See:
www.samplingplans.com/software_oc.htm
If you perform a search for the words "square root" (without quotes) in this forum, you will find other messages on the subject.
A more in-depth tutorial is here:
www.samplingplans.com/modern3.htm
Regards, Stan Hilliard