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November 29th, 2013, 05:31 AM  #1 
Joined: Oct 2009 Posts: 872 Thanks: 0  If (f(x) = e^x find ..
Hi I found 2 questions with answers in my handout. 1  If f(x) = e^x for x>0 find a) p(x = 3 ) b) p(x<4 ) I found the answer of this question for a = 0 but why?? for b the integration was from x= 0 to 4 why from 0 to 4 and we given in question x>0 so that mean x not become 0  2  If f(x) = x/8 for 3<x<5 find a) p(x<4) b) the mean of x Why for a the integration from 3 to 4 and we given that 3<x<5? b) How we can find mean? 
November 29th, 2013, 07:04 AM  #2  
Senior Member Joined: Sep 2007 Posts: 2,409 Thanks: 3  Re: If (f(x) = e^x find .. Quote:
Assuming that, then, by definition of "probability density function" and "cumulative probability functions", . Did you not know that? And, from that, . In particular, for any f(x). Quote:
Quote:
(You could think of this as but because f(x)= 0 for x< 3, that is the same as .) As for the mean, do you not know the definition of "mean" of a probability distribution? The mean value for probability density function f(x) is defined as . Here, since f(x) is defined to be x/8 for x between 3 and 5 (and 0 for all other x), that is dx= \frac{1}{8}\int_3^5 x^2 dx" />. Quote:
 
November 29th, 2013, 07:49 AM  #3 
Joined: Oct 2009 Posts: 872 Thanks: 0  Re: If (f(x) = e^x find ..
Thanks so much.


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