1. Feb 13, 2007 #1

   Physics is Phun

   

   I don't see how this is possible? how can you have a distrubution with no mean?
   My professor says there is, but i don't get it...

    

   Physics is Phun, Feb 13, 2007
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3. Feb 13, 2007 #2

   matt grime

   

   Science Advisor

   Homework Helper

   Exercise: find a series
   
   a_1+a_2+....
   
   that has a finite sum (and hence is can be made to have sum 1, and be a prob distribution on N) but where a_1+2a_2+3a_3+... is not finite (so there isn't a mean).
   
   And there are less contrived examples too.

    

   matt grime, Feb 13, 2007
4. Feb 13, 2007 #3

   mathman

   

   Science Advisor

   Gold Member

   Simple example a_k=1/k^2

    

   mathman, Feb 13, 2007

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