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Abstract
We establish alert and action limits for environmental monitoring programs in cleanrooms in the pharmaceutical industry. Heavily skewed count data, which exhibited both overdispersion compared to the Poisson distribution and an excess of zeroes, needed to be modelled. A hierarchical Poisson-gamma model is proposed for this purpose and compared to other models proposed in the literature, demonstrating a clear improvement in terms of fit and interpretation.
Additional information
Notes on contributors
Antje Christensen
Dr. Christensen is a Statistician. Her email address is [email protected].
Henrik Melgaard
Dr. Melgaard is a Statistician. He is a Member of ASQ. His email address is [email protected].
Jørgen Iwersen
Dr. Iwersen is a Statistician. He is a Member of ASQ. His email address is [email protected].
Poul Thyregod
Dr. Thyregod is a Faculty Member. He is a Senior Member of ASQ. His email address is [email protected].