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# Variance of the Sample Mean (Normal Population)

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Why bother with a post grad course - waste of time? 17-10-2016
1. Please see screenshot - Could someone please explain to the me steps.

In particular, why when taken outside of the sum does 1/n become 1/n2
Then after that why does the o2 come into play?
Help appreciated.
2. (Original post by JKITFC)
Please see screenshot - Could someone please explain to the me steps.

In particular, why when taken outside of the sum does 1/n become 1/n2
Then after that why does the o2 come into play?
Help appreciated.
If X is a random variable and a is a scalar, then . Just look at the formula for variance. The comes from the fact that the are identically distributed each with variance

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