From: Stan Hilliard
Date: 05 May 1999
Time: 23:49:22
Greetings Bill,
Your example confidence statement is equivalent to stating the consumers point of an OC curve. RQL=(100-90)=10%, consumer's risk=beta=1000ppm.
A sampling plan for attributes would require a sample of several thousand and with an acceptance number of Ac=0. The software program TP105 will develop such a plan. It uses the OC curve approach and also can calculate confidence limits based on either the binomial of the poisson distributions.
A sampling plan for variables, assuming normal distribution and standard deviation unknown, requires only about 25, with k=3.5(approx). The software program TP414 will develop such a plan. If you can use a known standard deviation plan, the sample size will go down to 4 or 5!
This example provides an excellent illustration of the difference between attributes and variables sampling. For more info on the software, see http://www.samplingplans.com/software_oc.htm
Sincerely, Stan Hilliard shilliard@samplingplans.com