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Thread: Building confidence intervals using Coefficient of variation

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    Building confidence intervals using Coefficient of variation




    Hi
    I have a doubt and i need to understand it.
    At my work, my colleagues use the coefficient of variation for doing confidence intervals.
    Not directly, obvious.
    They used this formula for the lower interval
    Code: 
    X-Z(95%)*X*Coefficient of variation/100
    .
    And i just don't get it.
    I've played with it and tried to take it to the class familiar way
    Code: 
    X-Z(95%)*Standard Deviation/Square Root(n)
    So, can you guide me?
    What am i forgetting to assimilate this new way of creating intervals?
    Thanks a lot for your replies and time.

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    Re: Building confidence intervals using Coefficient of variation

    Yeah, I am also not quite following. Are these data coming from a regression model or not?
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    Re: Building confidence intervals using Coefficient of variation

    It's a survey.

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    Re: Building confidence intervals using Coefficient of variation

    Just using data for a singe variable or is this from a more complex model?
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    Re: Building confidence intervals using Coefficient of variation

    For a single variable.

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    Re: Building confidence intervals using Coefficient of variation

    Well if I am following:

    X-Z(95%)*X*Coefficient of variation/100

    If Coefficient was calculated (x/sd)*100, then the above would give you:

    mean -(zscore*sd), which would be different from your standard approach since it would not directly address the sample size.
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    Re: Building confidence intervals using Coefficient of variation

    That's right. Where is the "Square root(n)"?
    If i am working with a population or a sample, does it make a difference in "Square root(n)"?

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    Re: Building confidence intervals using Coefficient of variation


    You will have to verify this, but isn't the SE of a population the SD.

    Are you treating your data as a sample or population?
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