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Re: Sampling plans for raw materials/chemicals

From: Stan Hilliard
Date: 22 Jan 2001
Time: 15:35:17

Comments

Hi Dave,

There is good methodology available for lot-by-lot variables sampling for chemical analyses. The materials can be in any form -- liquids, powders, pellets, etc. They can be packaged in bags, drums, bottles, etc.

The natural approach for homogeneous materials is to based the sampling plan on an oc curve for the mean. Typical examples would be sampling pure solutions or small containers that were filled from well-mixed larger containers.

Here are some sources of more information. You can print your own copies:

Sampling of Bulk Liquids, Powders, Pellets: www.samplingplans.com/outputvariablesmean.htm

Tutorial on applications (20 pages): www.samplingplans.com/modern3.htm

Using OC Curves to develop sampling plans: www.samplingplans.com/usingoccurves.htm

Software program TP414 ($245) supports both kinds of plan: 1) bulk materials based on OC Curves for the mean of the variable, and 2) individual items based on oc curves for the fraction of items not conforming to a specification limit(s). www.samplingplans.com/software.htm

TP414 also supports sequential sampling for variables. You use sequential sampling plans when it is important to use the smallest sample size possible.

Sincerely, Stan Hilliard


Last changed: November 20, 2007