From: Al Azur
Date: 8/21/2004
Time: 10:11:46 PM
Given valid economic information, a two-point method of designing an OC curve for a sampling plan could make perfect sense. The problem in practice is that this economic information is generally not available (for various reasons, some valid and some invalid). Consequently, the risks corresponding to these "two points" of proportion nonconforming on the OC curve tend to be arbitrarily decided in practice, starting off with ambitious values then being significantly compromised when the required sample size "appears" overly sizable and unpalatable.
While the point of this contribution was not to refute the so-called two-point method in general, it does call into question how it is actually practiced by uninformed and semi-informed practitioners.