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Homework Help: Basic Z-Score & Standard Normal Question

  1. May 7, 2008 #1
    If Z is a random variable having the standard normal distribution, find

    So I punch it into my calculator nmcdf(-.79,infinity,0,1) & I get the answer .7852

    The book however has the answer .2148 (essentially 1-ans).

    Which is what I don't understand...

    Have I forgotten something really simple, or do you think there is an error in the book. Most of the time its me :(.
  2. jcsd
  3. May 7, 2008 #2
    Also, P(-1.90>z>.44)

    The only thing I could think of was nmcdf(-infinity,-1.90,0,1)+nmcdf(.44,infinity,0,1) which gives .3587 but the book gives the answer .6143.
  4. May 7, 2008 #3


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    Are you sure you've written the problems correctly? P(-1.90>z>.44) is obviously zero, no matter how z is distributed.
    Last edited: May 7, 2008
  5. May 7, 2008 #4
    100% sure. I think its an error in the book... I don't really see how it can be possible. If you flip the signs around it makes sense though.
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