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Variable Sampling Interval Combined Shewhart–Cumulative Score Quality Control Procedure
Journal article   Peer reviewed

Variable Sampling Interval Combined Shewhart–Cumulative Score Quality Control Procedure

Raid W. Amin and Matoteng M. Ncube
Journal of the Royal Statistical Society: Series C (Applied Statistics), Vol.40(1), pp.1-12
1991

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Abstract

A standard combined Shewhart–cumulative score quality control scheme for controlling the process mean takes samples from the process at fixed length sampling intervals. This paper proposes a modification which varies the time intervals between samples depending on what is being observed from the data. The properties of the proposed variable sampling interval combined Shewhart–cumulative score scheme are evaluated using a Markov chain approach. Results show that the scheme proposed is considerably more efficient than either the standard combined Shewhart–cumulative score chart or the standard cumulative sum chart.

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