In this article, the quality of a process or product is assumed to be represented by a relationship (or profile) between the response variable and one or more explanatory variables. Due to the characteristic of the response variable, which is both categorical and ordinal, the relationship is better characterized by a proportional odds model. Two MEWMA-type control charts for monitoring such profiles in Phase II monitoring are proposed. Simulation studies are conducted to compare the effectiveness of these two charting schemes. Furthermore, a diagnostic method is employed to estimate the change point location of the process and to identify the parameters of change in the profile. Finally, a real example is used to illustrate the implementation of the proposed charting schemes and the diagnostic method.
