Results 1 to 3 of 3

Math Help - normal probability distributions

  1. #1
    Newbie
    Joined
    Oct 2009
    Posts
    2

    normal probability distributions

    heights are normally distributed with mean 63.6 in and standard deviation 2.5 in

    What percentage of women are at least 70 in?

    How would I go about doing this?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Rhymes with Orange Chris L T521's Avatar
    Joined
    May 2008
    From
    Chicago, IL
    Posts
    2,844
    Thanks
    3
    Quote Originally Posted by maria13always View Post
    heights are normally distributed with mean 63.6 in. and standard deviation 2.5 in.

    What percentage of women are at least 70 in?

    How would I go about doing this?
    Convert to Standard Normal:

    \mathbb{P}\!\left(X\geq 70\right)=\mathbb{P}\!\left(\frac{X-\mu}{\sigma}\geq \frac{70-63.6}{2.5}\right)=\mathbb{P}\!\left(Z\geq 2.56\right)

    Note that \mathbb{P}\!\left(Z\geq 2.56\right)=1-\mathbb{P}\!\left(Z<2.56\right)\approx.00523. This means that .523% of women are 70in or taller.

    Does this make sense?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member
    Joined
    Jul 2009
    Posts
    593
    Thanks
    4
    They tell us the distribution, so we know what particular distribution to use. You need to find out how many standard deviations 70 inches is from 63.6 inches. Do you know how to do this:

    \frac{\overline{x}-x}{\sigma_{x}}=z

    Do you know how to read a z-chart? Also carefully read the sentence. They are asking for what percentage of women are at LEAST ( P(X\geq70)) 70 inches.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Normal Probability Distributions....
    Posted in the Statistics Forum
    Replies: 1
    Last Post: March 29th 2011, 05:04 AM
  2. normal distributions/probability
    Posted in the Statistics Forum
    Replies: 1
    Last Post: October 18th 2010, 06:37 AM
  3. Stats Questions: Probability and Normal Distributions
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: December 15th 2008, 09:10 PM
  4. Conditional probability with normal distributions
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: October 22nd 2008, 03:13 AM
  5. Normal probability distributions
    Posted in the Advanced Statistics Forum
    Replies: 4
    Last Post: May 13th 2007, 09:52 PM

Search Tags


/mathhelpforum @mathhelpforum