Rejoinder

We thank the editor Professor David Steinberg for organizing this stimulating discussion. We are also grateful to all the discussants for their constructive comments about the method proposed in our paper (denoted as QZW hereafter). Profile monitoring is a relatively new research area; but, it has a profound application background (cf., Wang and Tsung 2005, Woodall et al. 2004). Due to the fact that the data structure in profile monitoring is much more complicated than that in conventional process monitoring problems, it is also a challenging task. In QZW, we try to apply some recent statistical tools developed in some other research areas, including longitudinal data and functional data analysis (e.g., Fitzmaurice et al. 2008, Liang and Zeger 2002), to the area of profile monitoring. As pointed out by the discussants, there are still some issues in our proposed method that need to be addressed in future research. In the next several parts, we provide our thoughts about some main issues raised by the discussants.