第二章预测技术，介绍定性与定量预测技术的特点和步骤，重点介绍灰色预测模型，为石油化工需求分析及港口吞吐量预测作理论支撑；
Chapter two is about the prediction technology . The characteristics and the processes of the qualitative and quantitative technology , especially the gray prediction model , are introduced .
定性预测技术