PERFORMANCE OF CONTROL CHARTS FOR SPECIFIC ALTERNATIVE HYPOTHE- SES

We present statistical models in terms of hypothesis testing for practical out-of-control situations in SPC that extend the traditional mean shift or linear trend situations. Based on these explicit alternative hypothe- ses, we derive likelihood ratio tests. Simulations are used to obtain critical values and to study the performance (in terms of both mean and standard deviation of detection delays) of our procedures. We compare our control charts with a control chart proposed by Chang and Fricker. It turns out that smaller mean delays are not always preferable. Acknowledgement: The work of the second and third author is partially sup- ported by grants GA ˇ