ARMA-GM combined forewarning model for the quality control

Three forecasting models are set up: the auto-regressive moving average model, the grey forecasting model for the rate of qualified products Pt, and the grey forecasting model for time intervals of the quality catastrophes. Then a combined forewarning system for the quality of products is established, which contains three models, judgment rules and forewarning state illustration. Finally with an example of the practical production, this modeling system is proved fairly effective.