—Cumulative count of conforming (CCC) chart has
been shown effective for high-yield processes with very low
fraction of nonconforming items. Traditional CCC chart
assumes the products from a process are inspected item by item.
Recently, the CCC chart was generalized to conform to the
industrial practice where items are inspected sample by sample
without according to the production order. Different from the
traditional chart, the generalized CCC chart monitors the
cumulative count of samples until a nonconforming sample is
encountered. In order to improve the power of the generalized
CCC chart to detect process changes, this study applied the
control scheme of variable sample size (VSS) to the generalized
CCC chart. The average time to signal (ATS) process change of
the proposed chart was derived by Markov chain approach and
taken as performance measure to evaluate its statistical
efficiency. Performance comparisons between the proposed
chart and generalized CCC chart are made to evaluate its
—Cumulative conformance count, variable
sample size, markov chain.
Y. K. Chen is with Department of Distribution Management, National
Taichung University of Science and Technology, 129, Sec 3, Sanmin Rd,
Taichung, Taiwan (e-mail: ykchen@ nutc.edu.tw).
C. Y. Chen is with Department of Electronic Engineering, National
Yunlin University of Science & Technolgy, 123, Sec 3, University Rd,
Douliu, Yunlin, Taiwan (e-mail: author@lamar. colostate.edu).
Cite:Y. K. Chen and C. Y. Chen, "Cumulative Conformance Count Charts with Variable Sample Sizes," International Journal of Trade, Economics and Finance vol.3, no.3, pp. 187-193, 2012.