沪深两市收益率具有尖峰、偏斜的特征,月度收益率比日收益率、周收益率更接近正态分布。剔除异常值之后,偏度下降,收益率更接近正态分布。在回归估计贝塔系数时,如果样本过小,应剔除异常的收益率值,以保证回归的有效性。
Returns of Shanghai and Shenzhen stock market have leptokurtichave and skewness.Distributions of monthly returns are more normal than daily and weekly returns.While extreme values are skipped,skewness gets down,and returns are more normal than before.When the samples of beta estimation by regression are too small,extreme values should be skipped.