# Median and variance

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Hi

I have a distribution for which I would like to use median say M. The problem is that I do not know how to define some range based on M+3 $\sigma$. Is there some kind of variance related to median ?

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Since you have the distribution why would you not simply calculate the variance from it?

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If it is a binomial distribution then:

$\mu=np$

$\sigma=(np(1-p))^{2}$

so $\sigma=(\mu(1-p))^{2}$

and in a normal distribution the medians is equal to the mean so you should be able to relate the two. Hope this helped.

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• 2 months later...

In general if your distribution is symmetrical, then the median and mean are the same. Remember that the 3 sigma rule relates to normal distributions. If you do not have a normal distribution then the 99.7% does not apply. The percent might be higher or lower - it all depends on your data.

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