A.S是σ的无偏估计
B.
C.
D.
[判断题]A.对B.错
[单选题]A.B.C.D.
[单选题]A.≤1/4B.≤8/9C.≤80/81D.≥8/9
[单选题]A.线性相关B.线性无关C.正交D.平行
[单选题]A.1B.2C.3D.4
[单选题]A.2B.2g′(a)C.2ag′(a)D.2bg′(a)