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Math Help - Help me please

  1. #1
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    Help me please

    Let x = age of employee . Assume x is normally distributed with a men of 38 and a standard of 9

    what fraction of employees are under the age of 40

    if one employee is picked at random, what is the probability that he will be under the age of 40.

    If a simple random sample of 100 employee is picked, what is the probability that the sample mean will be less than 40
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  2. #2
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    Quote Originally Posted by waterboy View Post
    Let x = age of employee . Assume x is normally distributed with a men of 38 and a standard of 9

    what fraction of employees are under the age of 40

    if one employee is picked at random, what is the probability that he will be under the age of 40.

    If a simple random sample of 100 employee is picked, what is the probability that the sample mean will be less than 40
    P(x<40) = P(z<\frac{40-\mu}{\sigma}) = P(z<\frac{40-38}{9}) = P(z<0.222)

    From here find a normal cdf table & you'll be in the money!
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  3. #3
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    is this correct

    39-38/9 =0.111 = 0.438

    40-38/9 = 0.22=0.871
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  4. #4
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    Quote Originally Posted by waterboy View Post
    is this correct

    39-38/9 =0.111 = 0.438
    This is all sorts of wrong, firstly

    39-38/9 = 34.78 \neq 0.111

    and

    0.111 \neq 0.438

    I think you mean to say

    \frac{(39-38)}{9} = 0.111

    then

    P(z < 0.111) = 0.54

    from Normal dist table. you really have to be careful with your order of operations!
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