If X ~ chi-square(k) then (2X)^0.5 is approximately normally distributed with mean (2k-1)^0.5 and unit variance (result credited to R. A. Fisher). 由这个和3.6可以推出3.8。我也没看明白书中的"using the same approximation”是什么意思。。。

The standard error is the standard deviation of the sampling distribution of a statistic. The term may also be used to refer to an estimate of that standard deviation, derived from a particular sample used to compute the estimate.

你的图片有点大，建议换成jpg格式。

谢谢啦，虽然我没太看懂，关于这部分不知道core reading上是否有讲解呢？

谢谢啦，虽然我没太看懂，关于这部分不知道core reading上是否有讲解呢？

样本均值的标准误可以看做样本均值误差的标准差，反应样本均值同总体均值的离散程度（误差情况）。

推导内容请参看维基百科：http://en.wikipedia.org/wiki/Standard_error_(statistics)

take a look~