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The Effect of Pooled and Un-pooled Variance Estimators of C(pm) When Using Subsamples

Summary: [This abstract is based on the authors' abstract.] In actual manufacturing practice, subsamples representing logical subgroups, rather than a single representative sample, are typically collected over time for the purpose of quality control. In light of this more realistic data structure, two C(pm) estimators corresponding to pooled and un-pooled variance estimators are evaluated and applied to hypothesis testing and power calculations. Power functions of these tests are used to determine the minimum number of subsamples needed. Tables provide recommended numbers and usage of subsamples.

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  • Topics: Process Capability, Sampling
  • Keywords: Multivariate capability indices,Hypothesis testing,Process capability (Cp),Sample estimates,Sample size
  • Author: Hubele, Norma Faris; Vannman, Kerstin
  • Journal: Journal of Quality Technology