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Math Help - Probability distribution

  1. #1
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    Probability distribution

    The marks of history in a test are normally distributed with a mean of 55 and a standard deviation of 8 .
    ( a ) if 10.2 % of the students failed History , find the minimum marks needed to pass







    ( b ) If 73.4% of the students scored a credit in History , find the minimum marks to score a credit
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  2. #2
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    Quote Originally Posted by mathaddict View Post
    The marks of history in a test are normally distributed with a mean of 55 and a standard deviation of 8 .
    ( a ) if 10.2 % of the students failed History , find the minimum marks needed to pass
    Let X be the variable and let Z be the normalised variable, such that Z = \frac{X-55}{8} at let W be the pass mark, so you know that P(X<W) = 0.102 \ \rightarrow P(Z< \frac{W-55}{8}) = 0.102 now you must reference your stats table (or use technology) to find the Z value corresponding to 0.102 and solve for W.

    Bobak
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  3. #3
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    thanks Bobak
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