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Sample and population variances: elementary question 
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#1
Jan3113, 01:15 AM

P: 557

Given a sample of a normally distributed population, then the sample variance ≈the population variance divided by the sample size. Nice. However, if one now increases the sample size to the population, this becomes that the population variance ≈ the population variance divided by the population size, which is absurd. What elementary concept am I missing here? Thanks in advance



#2
Jan3113, 01:38 AM

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P: 12,428

The idea is to estimate the population variance from a sample.
http://en.wikipedia.org/wiki/Varianc...ample_variance 


#3
Jan3113, 01:58 AM

P: 570

The population parameters are assumed to be constants. The sample parameters are random variables, because they will vary from sample to sample. You are also confusing the sample variance with the variance of the sample mean. The variance of the sample mean (usually) converges to zero, while of course the population variance does not. The sample variance converges to the population variance. This stuff is confusing, but it is important to get it straight or you will never understand statistics. So good for you for asking. 


#4
Jan3113, 02:48 AM

P: 557

Sample and population variances: elementary question
From ImaLooser
. And thanks also to Simon Bridge for replying. 


#5
Feb1513, 06:11 AM

P: 239

Sample variance is NOT equal to population variance divided by sample size.



#6
Feb1513, 07:55 AM

P: 557

ssd:



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