容量分别是n1,n2.组成一个联合样本n1+n2,组合样本的方差是?从总体中抽取两组样本,其容量分别为n1与n2,设两组的样本均值分别为 X1与X2,样本方差分别为S1^2及S2^2,把这两组样本合并为一组容
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容量分别是n1,n2.组成一个联合样本n1+n2,组合样本的方差是?从总体中抽取两组样本,其容量分别为n1与n2,设两组的样本均值分别为 X1与X2,样本方差分别为S1^2及S2^2,把这两组样本合并为一组容
容量分别是n1,n2.组成一个联合样本n1+n2,组合样本的方差是?
从总体中抽取两组样本,其容量分别为n1与n2,设两组的样本均值分别为 X1与X2,样本方差分别为S1^2及S2^2,把这两组样本合并为一组容量为n1+n2的联合样本,
容量分别是n1,n2.组成一个联合样本n1+n2,组合样本的方差是?从总体中抽取两组样本,其容量分别为n1与n2,设两组的样本均值分别为 X1与X2,样本方差分别为S1^2及S2^2,把这两组样本合并为一组容
组合样本的方差是 S1^2 + S2^2
This problem is not as simple as the answer suggests here. When combining m random variables: n1, n2, ..., nm each with an average value of X1, X2, ..., Xm and a standard deviation S1, S2, ..., Sm, the average of the new random variable N = n1 + n2 + ... + nm will have an average value of X = X1 + X2 + ... + Xm, this is expected. The standard deviation of the new random variable, though, is S = (S1^2 + S2^2 + ... + Sm^2)^(1/2). So the variance of the new random variable or Var(N) = S1^2 + S2^2 + ... + Sm^2