“…Relationships between the process variable and the covariates are called profiles, and various techniques have been suggested to monitor linear and nonlinear profiles. Some of these may be found in Ding et al, 1 Moguerza et al, 2 Williams et al, 3 Vaghefi et al, 4 Fan et al, 5 Fan et al, 6 Lee et al, 7 Chang et al, 8 and references therein. A good review of these techniques and assessment of their relative effectiveness may be found in Fan et al 6 As related therein, In this article, a third approach is suggested, which may be viewed as a hybrid of the parametric and the nonparametric approaches.…”