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The Adjusted p Chart and u Chart for Varying Sample Sizes

Summary: It is common to have control charts for fraction of nonconforming items or number of nonconformities that are based on differing sample sizes for each observation. This paper presents a simple method for charting such data that is as easy to interpret as a control chart for fixed sample size and that has the same chance for an observation to lie beyond the control limits as a control chart with limits computed separately for each observation.

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  • Topics: Statistics, Sampling
  • Keywords: Statistics,Control charts,Sample size,Poisson distribution
  • Author: Rocke, David
  • Journal: Journal of Quality Technology