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Title: On the estimation error in zero-inflated poisson model for process control
Authors: He, B.
Xie, M. 
Goh, T.N. 
Ranjan, P.
Keywords: Attribute chart
Average run length
Count data modeling
Zero-inflated Poisson distribution
Issue Date: Jun-2003
Citation: He, B.,Xie, M.,Goh, T.N.,Ranjan, P. (2003-06). On the estimation error in zero-inflated poisson model for process control. International Journal of Reliability, Quality and Safety Engineering 10 (2) : 159-169. ScholarBank@NUS Repository.
Abstract: The control chart based on a Poisson distribution has often been used to monitor the number of defects in sampling units. However, many false alarms could be observed due to extra zero counts, especially for high-quality processes. Therefore, some alternatives have been developed to alleviate this problem, one of which is the control chart based on the zero-inflated Poisson distribution. This distribution takes into account the extra zeros present in the data, and yield more accurate results than the Poisson distribution. However, implementing a control chart is often based on the assumption that the parameters are either known or an accurate estimate is available. For a high quality process, an accurate estimate may require a very large sample size, which is seldom available. In this paper the effect of estimation error is investigated. An analytical approximation is derived to compute shift detection probability and run length distribution. The study shows that the false alarm rates are higher than the desirable level for smaller values of the sample size. This is further supported by smaller average run length. In general, the quantitative results from this paper can be utilized to select a minimum size of the initial sample for estimating the control limits so that certain average run length requirements are met.
Source Title: International Journal of Reliability, Quality and Safety Engineering
ISSN: 02185393
DOI: 10.1142/S0218539303001068
Appears in Collections:Staff Publications

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