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Math Help - Help! Given normal distrib. w/ mean=100, stand. dev.=16. How to find p(below 120)?

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    Help! Given normal distrib. w/ mean=100, stand. dev.=16. How to find p(below 120)?

    help please!!!

    i'm not sure what to do! how would i find the probability below and also above 120?!


    i greatly appreciate any help!
    Last edited by beetz; October 17th 2007 at 07:56 AM.
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    is it P(random variable X < 120) for below 120? and P(X>120)
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    Quote Originally Posted by beetz View Post
    help please!!!

    i'm not sure what to do! how would i find the probability below and also above 120?!


    i greatly appreciate any help!
    What's the z score for 120 for this distribution?

    -Dan
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    z-score for 120 is 1.25

    i will be using a ti 83 to calculate this..
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    the z-score isn't my final answer, right?
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    help!!!
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    Forum Admin topsquark's Avatar
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    The z score tells you how much of the distribution you need to take to figure out the probability. You can't calculate it on a TI-83: the calculator does not have that capability. You need to look it up in a table.

    -Dan
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    holy cow. the text book never goes over a table....


    there are problems like this in my textbook P(X<40)=normcdf(-E99,40,75,3)


    would i just apply that here since i have no knowledge of using a table?
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    Forum Admin topsquark's Avatar
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    Quote Originally Posted by beetz View Post
    holy cow. the text book never goes over a table....


    there are problems like this in my textbook P(X<40)=normcdf(-E99,40,75,3)


    would i just apply that here since i have no knowledge of using a table?
    See one of your other posts. Apparently I was wrong about the TI-83. However, I am astonished that your instructor never taught you how to use the table and only expects you to be able to use your calculator...

    -Dan
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