Research
The Shewhart-Ewma Automatic Control Chart
As the amount of critical process data increases due to automatic data acquisition systems, two problems present themselves. First, it becomes uneconomic to add sufficient staff to monitor all these processes using control charts, and second, the skill level required to observe and interpret the control charts becomes an ongoing issue of assuring accuracy and consistency via expensive training programs. An automated control procedure could conceivably provide a solution to both of these issues.
A Comparison Test for Net Sensitivity
A common problem in supplier management involves being able to tell if the difference in quality performance between suppliers is significant. Net sensitivity is a process capability measure of the nonconformance risk associated with a supplier’s product or service performance. This paper provides a two-sample confidence interval test that will allow the practitioner to determine if there is a significant risk difference between two suppliers with respect to their net sensitivities.
Process Capability Analysis Using Curve Fitting Methods
This paper offers a new approach to process capability measurement based on techniques for estimating the fraction nonconforming in the tails of the observed process distribution. The methodology proposed can provide significantly more accurate results and applicability to a much larger class of process distributions than the standard approaches of calculating capability indices based on making parametric assumptions or using standard curve fitting techniques. The tail probability estimation approach to capability analysis can significantly enhance the practitioners understanding of the processes they are attempting to develop and/or control because it provides a more robust and accurate measure of capability. This clearer insight into process performance becomes increasingly important as the allowable fraction nonconforming levels decline.
