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st: AW: mean of a distribution


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: AW: mean of a distribution
Date   Sun, 18 Oct 2009 20:06:39 +0200

<> 


In this particular case, there is a shortcut to the mean which makes your
life easier. If no such shortcut existed, you would indeed have to calculate
the integral...



HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von carol white
Gesendet: Sonntag, 18. Oktober 2009 20:05
An: statalist@hsphsun2.harvard.edu
Betreff: st: mean of a distribution

Hi,
How to calculate the mean of the distribution of a random variable? Take the
exponential distribution with the probability density function
f(x)=lambda.exp(-lambda.x) where lambda is a constant and x is a random
variable. The mean of this distribution is the reciprocal of lambda. If the
mean is the expected value of x, which for a continuous random variable E(x)
= Integral (x.f(x))dx, how could E(x) be the reciprocal of lambda?

Regards,

Carol 


      
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