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Math Help - Markov's Inequality Problem Help! MIDTERM MONDAY!

  1. #1
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    Markov's Inequality Problem Help! MIDTERM MONDAY!

    Let X be uniformly distributed over (1,4)

    (a) Use Markov's inequlaity to estimate P(x>=a) a is between 1 to 4 and compare this result to the exact answer.

    (b) Find the value of a in (1,4) that minimizes the difference between the bound and the exact probability computed in (a).

    For this question i used
    EX= (a+b)/2 since its uniformly distributed so i got EX=5/2 which means that the probability of X being greater than or equal to a is less than 5/2a. For the exact value I got the dist function of a uniform RV as being (x-a)/(b-a) so the F(x) should be (a-1)/4. The exact value is 1-(a-1)/4 so i got the exact value as being (4-a)/3.(b) I had (4-a)/3 <= 5/2a and then got them to one side took the derivative and set it equal to 0 and got 2.738

    Was this right? Thanks!
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  2. #2
    MHF Contributor kalagota's Avatar
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    Quote Originally Posted by clipperdude21 View Post
    Let X be uniformly distributed over (1,4)

    (a) Use Markov's inequlaity to estimate P(x>=a) a is between 1 to 4 and compare this result to the exact answer.

    (b) Find the value of a in (1,4) that minimizes the difference between the bound and the exact probability computed in (a).

    For this question i used
    EX= (a+b)/2 since its uniformly distributed so i got EX=5/2 which means that the probability of X being greater than or equal to a is less than 5/2a. For the exact value I got the dist function of a uniform RV as being (x-a)/(b-a) so the F(x) should be (a-1)/4. The exact value is 1-(a-1)/4 so i got the exact value as being (4-a)/3.(b) I had (4-a)/3 <= 5/2a and then got them to one side took the derivative and set it equal to 0 and got 2.738

    Was this right? Thanks!
    as i read the arguments you did, nothing's wrong with it.. i think, it is correct..
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