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Homework Help: Simple Statistics Problem

  1. Oct 6, 2009 #1
    The question reads exactly as follows,

    Find the appropriate values for #'s.

    a) P(Z<#)=.9
    b) P(|Z|<#)=.9

    We are currently going over distributions, poissons, density functions and binomial stuff, someone referenced to Z-values from a ztable but i dont know if this is what the topic at hand is. Does anyone know what they are asking?
  2. jcsd
  3. Oct 7, 2009 #2


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    I assume Z is some random variable. What is its probability distribution?
  4. Oct 7, 2009 #3


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    It looks to me like they are asking "for what value of "#" is the probability that z is less than # equal to .9?" and "for what value of "#" is the probability that |z| is less than # equal to .9?" The answer, of course, will depend on the probability distribution. Since you refer to "z values" and a "z table" I suspect you are talking about a "normal distribution". Here is a table for the normal distribution:
    http://people.hofstra.edu/Stefan_Waner/realworld/normaltable.html [Broken]

    Notice that this gives the probabilty that z is between 0 and the given number. To find the probabilty that z is less than a number, look up the value and add 0.5. To find the probability that |z| is than than the number, look up the value and multiply by 2.
    Last edited by a moderator: May 4, 2017
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