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S2 Normal Distribution help

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    Hi, I came across this question in the ocr textbook and I'm a bit stuck. Could someone show me how to do it please? It's from Ex 2B p.34

    7 (e) Given that X~N(15,4), find s,t,u,v and w correct to 2 d.p.

    P(|X-15| < w) = 0.9

    The answer is 3.29 but I don't know how to get there!
    Thanks very much
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    (Original post by Cometflute)
    Hi, I came across this question in the ocr textbook and I'm a bit stuck. Could someone show me how to do it please? It's from Ex 2B p.34

    7 (e) Given that X~N(15,4), find s,t,u,v and w correct to 2 d.p.

    P(|X-15| < w) = 0.9

    The answer is 3.29 but I don't know how to get there!
    Thanks very much
    What have you tried?
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    (Original post by RDKGames)
    What have you tried?
    I know that you use z=(x-15)/2 and 15 is the mean so the graph should be like the Z graph except a different height. I tried doing P(|X-15|<w) = 2x P(Z<w) -1 so P(X<w/2) = P(Z<1.282) but that didn't give me the right answer. Maybe you're meant to introduce s= |X-15| for example? But I'm still not sure how to go about solving that...
 
 
 
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