1. When some main fac tors change, there is uncertainty in economic forecast if the forecast method is used as usual. 经济预测中发生主要影响因素改变时，若采用通常的预测方法会因历史数据过少而出现较大误差。
2. Objective to identify the cause and transmission route of hepatitis a, to analyse the epidemic fac - tors and to evaluate the control effect. 目的查明甲肝暴发原因和传播途径，分析流行因素，评价控制效果。
3. Objective to understand the current status of sports behavior of workers in Shenzhen City from outside and the fac-tors affecting their regular sports. 目的了解深圳市外来劳务工运动行为现状及影响其进行有规律运动的因素。
4. The testing instrument of telephone outside connections is a set of instruments for examining and testing telephones and feed lines by telephone exchange station opera-tors. 电话外线测试仪，是电话交换台对用户话机、馈线进行检查、测试的配套仪器。
