In the field of statistical process control, Shewhart's charts are widely recognized as a simple and effective tool to judge whether a production process can be considered, at a given time and with reference to a characteristic being monitored, either in statistical control or out of control. The simplicity of the method, however, goes to the detriment of the information which can be gathered from the cumulative results of earlier observations which would make it possible to discern possible trends of sample observations approaching the control limits; in literature, we may find several alternative methods, such as, for instance, CUSUM or EWMA. In the following we shall introduce a scheme based on two pairs of gauges that improves the sensitivity of Munford's cumulative score chart for detecting a large shift in the mean, and this in the sense that when the process is out of control, observations with higher scores will be more likely to appear and they may be detected more quickly. We applied these control charts to monitoring the montly coin-in and the earning processes of several slot-machines operating in an ufficial italian Casino.
A Two Pairs of Gauging Scores Control Chart to Monitoring the Process of Slot Machines
DURIO, Alessandra;ISAIA, Ennio Davide
2003-01-01
Abstract
In the field of statistical process control, Shewhart's charts are widely recognized as a simple and effective tool to judge whether a production process can be considered, at a given time and with reference to a characteristic being monitored, either in statistical control or out of control. The simplicity of the method, however, goes to the detriment of the information which can be gathered from the cumulative results of earlier observations which would make it possible to discern possible trends of sample observations approaching the control limits; in literature, we may find several alternative methods, such as, for instance, CUSUM or EWMA. In the following we shall introduce a scheme based on two pairs of gauges that improves the sensitivity of Munford's cumulative score chart for detecting a large shift in the mean, and this in the sense that when the process is out of control, observations with higher scores will be more likely to appear and they may be detected more quickly. We applied these control charts to monitoring the montly coin-in and the earning processes of several slot-machines operating in an ufficial italian Casino.
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