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Use of Augmented Box Plots for Reviewing Measurement Results Collected Over Time

Summary: It is customary to summarize physiologically "normal" laboratory values as the 2.5th and 97.5th percentiles of the control animals, found separately for males and females of selected age groups, and covering data collected over specific intervals of time, perhaps the last six months, or the last three years. Such values may then be updated every six months. Toxicologists must often decide whether to characterize laboratory values from treated animals as falling within the physiologically "normal" range. This is aided by reference would be made to the six-month record representing the more current control values. notched box plots provide a convenient device for determining the stability of control data from individual experiments carried out over time. a procedure has been developed that allows such a determination from data pooled over both males and females and over all age groups. To cut down on the amount of data to be displayed by computer print-out, a procedure has been devised that will limit the print-out only to cases that show some measure of unusual instability over time. The procedures discussed in this paper afford a simple way to review masses of measurement results collected over time from any continuous operation.

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  • Topics:
  • Keywords: Box plots,Measurement and control,Values,Statistical methods,Graphical methods
  • Author: Ciminera, Joseph L.; Tukey, John W.
  • Journal: Journal of Quality Technology