432统计学真题及答案
B.\hat { \mu }= \frac {1}{5}X_{1}+\frac {2}{5}X_{2}+\frac {1}{5}X_{3}+\frac {1}{5}X_{4}C.\hat { \mu }= \frac {1}{9}X_{1}+\frac {2}{9}X_{2}+\frac {1}{9}X_{3}+\frac {1}{9}X_{4}D.\hat { \mu }= \frac {1}{3}X_{1}+\frac {1}{3}X_{2}+\frac {1}{6}X_{3}+\frac {1}{6}X_{4}7.抛掷一枚均匀的硬币1000次,则正面出现次数在484到516之间的概率约为()。A.0.68B.0.75C.0.90D.0.958.设总体X \sim N(0,1),X_{1},X_{2}, \cdots ,X_{n}(n>1)为来自总体X的一个样本,X,S^{2}分别为样本均值和样本方差,则有()。A.\overline {X} \sim N(0,1)B.n \overline {X} \sim N(0,1)C.\frac { \overline {X}}{S} \sim t(n-1)D.\sum _{i=1}^{n}X_{i}^{2} \sim X^{2}(n)9.设0,1,0,1,1,1,0,1为来自总体B(1,p)的样本观察值,则p的矩估计值为()。A.\frac {1}{8}B.\frac {3}{8}C.\frac {5}{8}D.\frac {7}{8}10.若X \sim t(n),\frac {1}{X^{2}} \sim()。A.F(n,1)B.F(1,n)C.x^{2}(n)D.t(n)11.在假设检验中,当样本容量一定时,若缩小犯第一类错误的概率,则犯第二类错误的概率会相应()。A.增大B.减少C.不变D.不确定12.当σ未知时,正态总体均值μ的置信度为1-a的置信区间的长度为()。A.\frac {2S}{ \sqrt {n}}t_{a}(n)B.\frac {2S}{ \sqrt {n}}t_{ \frac {a}{2