![]() The first decision is whether the samples pass the 12s rule. These could be 2 measurements on one control material or 1 measurement on each of two different control materials. ![]() The table below shows the notation using subscripts.Ī decision tree (below) is used to determine if the multiple samples collected when control was done can be released.įor this example, 2 samples are collected (N=2). Short hand notations are used to abbreviate different decision criteria or control rules, such as 12s to indicate 1 control measurement exceeding 2s control limits. ![]() The rules are applied to the Levey-Jennings Chart instead of the traditional Shewhart individuals control chart, which uses slightly different calculations for the control limits. The rules were originally developed by James Westgard. They are based on the Western Electric Rules and Nelson Rules, but are modified for multiple samples in a laboratory setting. The Westgard rules are used for laboratory quality control using “runs” consisting of measurements of multiple samples (typically 2-4 samples), called multi-rule.
0 Comments
Leave a Reply. |