Distribution-Free Phase I Control Charts for Subgroup Location

• Autores: L. Allison Jones-Farmer, Victoria Jordan, Charles W. Champ
• Localización: Journal of quality technology: A quarterly journal of methods applications and related topics, ISSN 0022-4065, Vol. 41, Nº. 3, 2009, págs. 304-316
• Idioma: inglés
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• Resumen

  • Statistical quality control often relies on the completion of a Phase I study. Many Phase I control charts, however, rely on an assumption of normally distributed process observations that may not be reasonable in the early stages of process control. A literature review shows no purely distribution-free Phase I control chart methods currently exist. This study introduces a distribution-free method for defining the in-control state of a process and identifying an in-control reference sample that can be used to estimate the process parameters for a Phase II procedure. The proposed procedure compares favorably with the traditional X-bar chart when the process is normally distributed and better than the X-bar chart when the process distribution is skewed or heavily tailed.