control limits
"Limits on a control chart which are
used as criteria for signalling the need for action, or for judging
whether a set of data does or does not indicate a 'state of control'"
[ASQ]. Used here to refer to the defined limits or ranges of results
expected due to the random error of the method, and beyond which some
course of action should be taken. It is common in clinical laboratories
to use Levey-Jennings control charts with limits set as either the mean
plus or minus 2 standard deviations, or the mean plus or minus 3
standard deviations.
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