Service quality is becoming a strategic factor to retain existing customers and acquire new ones. It can be directly related to the extent to which the service successfully fulfills the needs of a customer and is often measured through questionnaires that are submitted to a population of customers. Different approaches have been proposed in the literature to analyze collected data. This paper p...

Assuming a first-order auto-regressive model for the auto-correlation structure between observations, in this paper, a transformation method is first employed to eliminate the effect of auto-correlation. Then, a maximum likelihood estimator (MLE) of a step change in the parameters of the transformed model is derived and three separate EWMA control charts are used to monitor the parameters of th...

We developed a multivariate moving average control chart to monitor the mean vector of a multivariate process in this study. The proposed chart is based on Hotelling’s 2 T statistic. A simulation study is conducted to evaluate the average run length performance of the proposed chart. The proposed chart performs better than Hotelling’s 2 T chart, 2 T chart with runs rules and the synthetic 2 T c...

In the previous two Chapters, we proposed fraction nonconforming nonparametric control charts to monitor process location and process variability. It is also shown that performance of proposed control charts are superior to that of the Shewhart X and sign charts. If process is running in an in-control state for a long period, it will reach in steady-state mode. In order to characterize long-ter...