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 Probability and Statistics Basic Probability and Statistics Math Forum

 October 23rd, 2017, 04:38 AM #1 Senior Member   Joined: Jan 2016 From: Blackpool Posts: 104 Thanks: 2 expectation question help if u=expectation(x) find expectation(x^2) would the answer just be u^2 or do i need more information, thanks! October 23rd, 2017, 05:01 AM #2 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,834 Thanks: 650 Math Focus: Yet to find out. Is that the entire question? We could possibly express $E(X^2)$ in terms of the variance. But I've been wrong before . $\sigma_X^2 = E(X^2) - \mu_X^2 \implies E(X^2) = \sigma_X^2 + \mu_X^2$ And no, E(X^2) definitely does not equal E(X)^2 ! Thanks from Jaket1 October 23rd, 2017, 06:08 AM #3 Senior Member   Joined: Jan 2016 From: Blackpool Posts: 104 Thanks: 2 Thankyou! The question actually is this: https://imgur.com/a/YbZw2 so i expanded out the rth moment of skewness and was wondering how i could elimate the e(x^2) and e(x) terms so ur reply helps a lot.  October 23rd, 2017, 06:16 AM #4 Senior Member   Joined: Jan 2016 From: Blackpool Posts: 104 Thanks: 2 thanks i have completed the question  October 23rd, 2017, 10:59 AM #5 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 Example: Suppose x can take on the values 0, 1, and -1 with probability 1/3 each. Then the expected value of x is E(x)= -1(1/3)+ 0(1/3)+ 1(1/3)= 0. u= x^2 takes on the values 0^2= 0, 1^2= 1 and (-1)^2= 1 with probability 1/3 each. That is the same as saying "0 with Probability 1/3 and 1 with probability 2/3". The expected value of u= x^2 is E(u)= 0(1/3)+ 1(2/3)= 2/3. Thanks from Jaket1 Tags expectation, question Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post nikozm Algebra 3 December 18th, 2013 01:07 PM eulerrules1 Advanced Statistics 6 December 9th, 2011 09:04 PM hendaz Algebra 2 May 23rd, 2010 01:57 PM hendaz Advanced Statistics 1 May 18th, 2010 01:13 PM nibblebot Advanced Statistics 1 October 30th, 2007 12:05 PM

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