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October 21st, 2017, 09:36 AM  #1 
Senior Member Joined: Jan 2016 From: Blackpool Posts: 100 Thanks: 2  Can Probability density functions take negative values?
My question is: evaluate the pdf at fx(3) where fx(x)=(2)/((1+x)^3) and compute value 1/32, can pdf's be negative or have i made a mistake in the previous question? Thanks!

October 21st, 2017, 09:40 AM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 2,311 Thanks: 1224 
pdf's can't be negative anywhere in their support. you've made a mistake somewhere. 
October 21st, 2017, 02:25 PM  #3 
Global Moderator Joined: May 2007 Posts: 6,684 Thanks: 658  Your f(x) is impossible. The definition of a density function requires it to be nonnegative for all x and integrate to 1.


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density, functions, negative, probability, values 
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