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Math Help - probability problem with standard deviation & mean.

  1. #1
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    probability problem with standard deviation & mean.

    Can someone please help me with this problem, I would really appreciate it!

    The weights of adult long-tongued fruit bats are known to be normally distributed with a mean of 20.22 grams and a standard deviation of 3.23 grams. What is the probability that a randomly selected bat will:
    a) weigh at most 15 grams?
    b) weigh less than 30 grams?
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  2. #2
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    Re: probability problem with standard deviation & mean.

    Do you have a scientific calculator?
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  3. #3
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    Re: probability problem with standard deviation & mean.

    yes
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  4. #4
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    Re: probability problem with standard deviation & mean.

    Do you have access to a Q function table and know how to use it? If the random variable X has the mean \mu and standard deviation \sigma, then F(X \leq x)=Q\left(\frac{x-\mu}{\sigma} \right)

    The two questions basically ask the same thing with different wording (just replace x in the formula).
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  5. #5
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    Re: probability problem with standard deviation & mean.

    Under distribution on the calculator
    normalcdf (left minimum, right maximum, mean, stand dev )
    Use -10000 for far left and 10000 for far right so that you get all the area that you can under the normal distribution.
    Example: for B normalcdf(-10000,30,20.22,3.23)
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