On the Sample Size Problem for X and X Shewhart Control Charts for a Mean and Implications for Designing Q-charts
نویسنده
چکیده
In this work we study the question of how much data is required in order for classical X and X charts with estimated control limits to perform essentially like charts with the true control limits. The results indicate that using estimated control limits results in charts on which the events that individual points exceed control limits are dependent events, and that one result of this dependence is to increase the rate of false alarms after short runs, even though the ARL is increased. The important implications of this to designing Q-charts is discussed.
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