Results 1 to 3 of 3

Math Help - Normal distribution problem...

  1. #1
    Newbie
    Joined
    Mar 2010
    From
    u.s.a
    Posts
    3

    Question Normal distribution problem...

    A normal distribution has a mean of 50 and a standard deviation of 4. Determine the value below which 95% of the observations will occur. In the book it says that the answer is X=56.60, but I have no clue how they got that.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    Normalize.

    P(X< x)= P(\frac{X-\mu}{\sigma} < z)

    Then via z-score tables find when P(\frac{X-\mu}{\sigma} < z) \approx .95 and use the corresponding x value
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Mar 2010
    From
    Mumbai
    Posts
    91
    Thanks
    2

    Lightbulb it goes like dis...

    u know mean (μ) =50 and s.d (σ) =4
    1-∝=95%

    now according to normal dist"-

    Z=[(x-μ)/σ ]~N(0,1)

    using porbabily p(Z<1.645)=0.95

    p((x-50)/4<1.645)=0.95

    by simplifing p(x<56.58)=0.95
    therefore x=56.58 when value below 95%of observations occur.

    P.S: 1.645 is a table value if u take it as 1.65 u get answer as 56.60

    hope it would help u..
    thank u
    amul
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. problem of normal distribution
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: December 6th 2009, 02:14 AM
  2. Normal Distribution Problem.
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: September 7th 2008, 12:28 AM
  3. Another Normal Distribution Problem
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 17th 2008, 12:01 PM
  4. Normal Distribution Problem
    Posted in the Advanced Statistics Forum
    Replies: 4
    Last Post: April 17th 2008, 11:04 AM
  5. Normal Distribution problem
    Posted in the Statistics Forum
    Replies: 2
    Last Post: October 8th 2007, 01:51 AM

Search Tags


/mathhelpforum @mathhelpforum