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Math Help - Help! standard deviation

  1. #1
    vhartless
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    Help! standard deviation

    Can anyone help me with the following questions? My daughter was up all night and I'm not with it today! THANKS!!!!

    A normal distribution has a mean of 21.8 and a standard deviation of 1.4. What is the z score for a value of 18.3?

    A normal distribution has a mean of 36 and a standard deviation of 3. What is the z score for a value of 42?

    For a standard normal distribution, 95% of the data are within _____ standard deviations of the mean.

    Using the region under the curve in a standard normal distribution, the cumulative area from the left for a z score of -1.645 is:?
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  2. #2
    Eater of Worlds
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    A normal distribution has a mean of 21.8 and a standard deviation of 1.4. What is the z score for a value of 18.3?
    z=\frac{x-{\mu}}{\sigma}=\frac{18.3-21.8}{1.4}

    A normal distribution has a mean of 36 and a standard deviation of 3. What is the z score for a value of 42?
    Same as above.

    For a standard normal distribution, 95% of the data are within _____ standard deviations of the mean.
    This is the 68-95-99.7 rule. 68% of the data is within 1 standard deviation of the mean. 95% is within 2 standard deviations of the mean and 99.7% of the data is within 3 standard deviations of the mean.

    Using the region under the curve in a standard normal distribution, the cumulative area from the left for a z score of -1.645 is:?
    Look up what corrsponds to -1.645 in the body of the z-table. It should be in your daughters stats book. Possibly in the front cover.
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