[SciPy-User] from 50% probablity value to standard deviation

[David Baddeley]

Hi Johannes,

I guess what you're talking about is the inter-quartile range - if you know that 
your data is normally distributed the std deviation and IQR are related by a 
constant factor:

IQR ~ 1.349\sigma (see wikipedia article on interquartile range, can also easily 
be derived from the gaussian CDF)

cheers,
David


----- Original Message ----
From: Johannes Radinger <johradinger at googlemail.com>
To: SciPy-User at scipy.org
Sent: Tue, 19 July, 2011 9:38:17 PM
Subject: [SciPy-User] from 50% probablity value to standard deviation

Hello SciPy-People,

I have got a normal distribution with μ=0 and I know that 50% of all
observations
are within a certain range (50% probability are between -x and +x).
How can I get the standard deviation of that normal distribution?
Usually 68,3 % are within one SD. How is it possible to calculate the
SD from my 50% value? Is there any conversion factor I can use? Can
that be simply and exactly calculated with Scipy?

Thank you

/Johannes
_______________________________________________
SciPy-User mailing list
SciPy-User at scipy.org
http://mail.scipy.org/mailman/listinfo/scipy-user