sample variance与sampling variance的区别

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sample  variance 是样本方差

sampling  variance是抽样方差，


请问这两个概念有什么区别？最好举个例子。谢谢。

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关键词：variance Sampling varian Sample ance Sampling Sample variance

Sample variance is just for the samples you have, it is a straight and fixed quantity.  For example, you have data x1 x2  .......x100, and the mean of these xs is xbar. Then, the sample variance ( the sample variance we refer to most often) is sum((xi-xbar)^2).

But sampling variance would be the sample variance of the samples we get by certain sampling methods, like selecting from samples we already have, or by generating new ones according to the information we have, like bootstrap, permutation. It can be un-fixed, depending on our generating methods.

还是没有太明白，

不过还是非常感谢，

lyxyb 发表于 2010-10-9 16:33
sample  variance 是样本方差

sampling  variance是抽样方差，


请问这两个概念有什么区别？最好举个例子。谢谢。

Here is my understanding,

sample  variance 是样本方差 is a measure of a given sample

sampling  variance是抽样方差 is a measure of a sampling method. Under a random sampling method, its variance will be reduced by square root of N.

lyxyb 发表于 2010-10-9 16:33
sample  variance 是样本方差

sampling  variance是抽样方差，

我认为一样.。

ltx5151 发表于 2010-10-9 16:40
Sample variance is just for the samples you have, it is a straight and fixed quantity.  For example, ...

这个解释更专业。