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Math Help - pet statistics

  1. #1
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    pet statistics

    Students in a class were asked to report the number of pets of their family

    # pets frequency
    1 3
    2 19
    3 16
    4 9
    47

    I figured the frequencies from the data provided but how do you calculate the sample mean and sample standard deviation?
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  2. #2
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    Quote Originally Posted by laser View Post
    Students in a class were asked to report the number of pets of their family

    # pets frequency
    1 3
    2 19
    3 16
    4 9
    47

    I figured the frequencies from the data provided but how do you calculate the sample mean and sample standard deviation?
    To calculate sample mean from a frequency table, read The Sample Mean

    To calculate sample variance from a frequency table read Learning Resources: Statistics: Power from Data! Variance and standard deviation (go down about half way).
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  3. #3
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    Thank you for the information. If I interpreted it correctly, I believe the mean is 125/47.

    1*3+2*19+3*16+4*19=125
    mean=125/47

    I don't think I got the standard deviation right

    [(1-125/47)^{2}*(3/47)]+[(2-125/47)^{2}*(19/47)] +[(3-125/47)^{2}*(16/47)]+[(4-125/47)^{2}*(9/47)]=1624/2209

    1624/2209=0.73517
    SD= \sqrt{0.73517}=0.85740

    Is this correct?
    Last edited by laser; April 11th 2009 at 02:34 PM.
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