The study methods include even study (to the first hypothesis), the comparison analysis (to the second and the first hypothesizes) and the multi-linear regression model (to the third hypothesis).

• 检验方法包括对第一个假设运用事件研究和双样本均值t检验，对第二个假设分别针对与行业的对比采用成对样本均值t检验和针对与增发的对比采用双样本均值t检验，对第三个假设采用多元线性回归模型，并使用逐一删除的统计筛选法。