Results 1 to 4 of 4

Math Help - Zscore/Standard Normal Probabilities

  1. #1
    Newbie
    Joined
    Jan 2009
    Posts
    21

    Zscore/Standard Normal Probabilities

    Given:
    mu = 65.7
    sigma = 15
    Standard normal distribution

    Question:
    20% of the area will be less than what x value?

    I looked at my z-score table and couldn't find .0200 so now I have no clue how to even begin!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    From your z-score table P(z< -0.8416)= .2

    Use this fact in z = \frac{x-\mu}{\sigma} \implies -0.8416 = \frac{x-65.7}{15} to solve for x
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2009
    Posts
    21
    Where did you get .8416? Could you possibly have a more complete z-score table or am I missing some intermediary calculation?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    Joined
    Jul 2009
    Posts
    593
    Thanks
    4
    Quote Originally Posted by tom ato View Post
    Where did you get .8416? Could you possibly have a more complete z-score table or am I missing some intermediary calculation?
    You could just as easily use -0.84. There is no missing step here, and you no doubt are meant to use -0.84.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. standard normal distribution
    Posted in the Statistics Forum
    Replies: 1
    Last Post: October 19th 2009, 01:25 PM
  2. Probabilities and Standard Deviations
    Posted in the Statistics Forum
    Replies: 8
    Last Post: June 10th 2009, 09:49 PM
  3. Replies: 0
    Last Post: May 24th 2009, 08:23 AM
  4. Standard Normal Distribution
    Posted in the Statistics Forum
    Replies: 1
    Last Post: November 12th 2008, 04:43 PM
  5. standard normal
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: November 4th 2007, 04:27 AM

Search Tags


/mathhelpforum @mathhelpforum