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    chi square with percentages




    Hello
    I have two sample with a very different size (n=42 and n=282) and I only know the percentages of the dependent variable (with 8 levels).

    The difference between the two sample in each level of DV is very large (for example: in the first condition the percentages are 16% and 82% respectively).

    I converted the percentages in observed frequencies (for example 16/100*42; 82/100*282; ect.). I performed a chi square 2x8 with spss and the p-value is not significant.
    How it is possible that p-value is not significant if the differences between the frequencies of each condition are vary large? This is not the procedure to be followed when you only have the percentages?

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    Re: chi square with percentages

    Your approach seems fine. Can you post your final constructed 2X8 table so we can provide a better response on the rationale?


    Thanks.
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    Re: chi square with percentages

    Quote Originally Posted by hlsmith View Post
    Can you post your final constructed 2X8 table so we can provide a better response on the rationale?


    Thanks.
    I posted a xlsx file with 2x8 table. Thanks.
    Attached Files

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    Re: chi square with percentages

    Sorry, I don't open online files


    What could be happening is that the test is under-powered, given the two distributions are truly different.
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    Re: chi square with percentages

    Quote Originally Posted by hlsmith View Post
    test is under-powered.
    sorry, what does it mean. test is not correct?

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    Re: chi square with percentages

    It would mean the two distributions (proportions for categories) are truly different, but you do not have enough data to make this conclusion. This would be a Type II Error, failing to reject the null hypothesis of no difference in distributions in the sample when the two distributions are truly different in the population.
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    Re: chi square with percentages


    thanks vary musch. Can I performe a different statistic to see if I have the same result?

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