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Math Help - Variable of a population

  1. #1
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    Variable of a population

    A variable of a population has a mean of 35 and a standard deviation of 42.

    a. If the variable is normally distributed, identify the sampling distribution of the sample mean for samples of size 9.
    b. Can you answer part a if the distribution of the variable under consideration is unknown?
    c. Can you answer part a if the distribution of the variable underconsideration is unknown but the sample size is 36 instead of 9?

    I have, for part a, the mean is 35 and standard deviation 14, but I'm not sure about parts b and c. I have only worked with normal distribution, how do you figure when distribution is unknown?
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    Quote Originally Posted by sjenkins View Post
    A variable of a population has a mean of 35 and a standard deviation of 42.

    a. If the variable is normally distributed, identify the sampling distribution of the sample mean for samples of size 9.
    b. Can you answer part a if the distribution of the variable under consideration is unknown?
    c. Can you answer part a if the distribution of the variable underconsideration is unknown but the sample size is 36 instead of 9?

    I have, for part a, the mean is 35 and standard deviation 14, but I'm not sure about parts b and c. I have only worked with normal distribution, how do you figure when distribution is unknown?
    Is there a requirement on sample size if the population is not known to be normal .....?
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    There is no requirement.
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    Quote Originally Posted by sjenkins View Post
    There is no requirement.
    I don't think you understood the point of my question.

    The answer is Yes there is a requirement on sample size if the population is not known to be normal ........
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  5. #5
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    OH, now I feel stupid

    I had actually sat down and really pressed myself and got the answer which is what you you got. I read with large sample sizes that it tends to become more normal so you would definitely need a large sample size.

    Thanks for your help though.
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