Results 1 to 4 of 4

Math Help - If X is a normal variate

  1. #1
    Banned
    Joined
    Dec 2009
    Posts
    24

    If X is a normal variate

    If X is a normal variate with mean 30 and standard deviation 5, find the probability that
    i) 26<x<40
    ii) x>45
    iii) |x-30|>5

    Solution :
    \mu = 30
    \sigma = 5

    am stuck on hw to solve the problem
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jul 2009
    Posts
    593
    Thanks
    4
    X comes from a population that is normally distributed. Therefore with a mean of 30 and a standard deviation of 5, you can easily convert your other statistics into Z-scores to calculate applicable probabilities. For the absolute value one, just create an interval like you normally would for absolute value: |x-30|<5 = 25<X<35.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Banned
    Joined
    Dec 2009
    Posts
    24
    Quote Originally Posted by ANDS! View Post
    X comes from a population that is normally distributed. Therefore with a mean of 30 and a standard deviation of 5, you can easily convert your other statistics into Z-scores to calculate applicable probabilities. For the absolute value one, just create an interval like you normally would for absolute value: |x-30|<5 = 25<X<35.
    i am having trouble with starting the question .....I dont know what the first step should be ......
    do u mean i integrate the from 26 to 40 for x ...........but i dont even know the value of f(x)
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by wolfyparadise View Post
    i am having trouble with starting the question .....I dont know what the first step should be ......
    do u mean i integrate the from 26 to 40 for x ...........but i dont even know the value of f(x)
    For part (iii), |x-30|>5 is equivalent to X > 35 or X < 25. And since the mean is 30, you can use symmetry to reduce the calculation: Pr(X > 35) + Pr(X < 25) = 2 Pr(X > 35) = 2 (1 - Pr(X < 35)) = 2 - 2 Pr(X < 35).

    Now ...... surely you have been taught how to convert from a normal variable X to a standard normal variable Z. And you will have been taught how to calculate probability from a standard normal distribution (tables, technology, etc.). These are all routine questions - you will have examples in class notes and your textbook. Furthermore, the forum has dozens of worked examples. MHF is not a substitute for you going back to your classnotes and textbook and doing the necessary reading an revision.

    If you need more help, please show that you have made some effort to nderstand the material. Show your work. Say specifically where you are stuck.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. bi-variate normal?
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: September 7th 2011, 02:14 AM
  2. Multi variate normal
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: August 8th 2010, 12:39 PM
  3. Uniform Variate
    Posted in the Advanced Statistics Forum
    Replies: 9
    Last Post: December 9th 2009, 04:15 AM
  4. Replies: 0
    Last Post: May 24th 2009, 08:23 AM
  5. Distribution of the variate Y
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: May 4th 2009, 04:46 PM

Search Tags


/mathhelpforum @mathhelpforum