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    tests of agreement between diagnostic tests

    I need to assess agreement between to variables. The problem is that one of the variable is a continuous variable and the other is a categorical variable. I create a test that gives a certain value to a the compression of the brain. The gold standard test gives a categorical value among compressed, non compressed and partially compressed. I dont know what test could help to probe an agreement between theses variables. Ive been told to use a Balnd-altman plots for my purpose. What do you think?

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    Re: tests of agreement between diagnostic tests

    So you have a screening diagnostic (continuous) variable and a binary gold-standard, correct. What types of values does the continuous predictor provide? If it provides predictive probabilities why not use those. I can think of multiple options, but I think you need to provide some more information first.


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    Re: tests of agreement between diagnostic tests

    Thanks for you answer. Let me explain this problem better.

    As I said before, brain compression is classically classified among "Compressed" - "Non Compressed" and "Partially Compressed"

    We generate a compression ratio that gives a numerical value for the compression. This ratio takes values between 0 and 1 meaning 0 is absolutely compressed and 1 means absolutely non compressed (in fact this value es not possible because it would mean that there's no brain in this area).

    I have to show that there is a correlation between these variables.

    Does this make sense to you?

    Thanks

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    Re: tests of agreement between diagnostic tests

    You didn't say correlated before. Check out the "Point-Biserial Correlation Coefficient".


    If not check out:




    Spearman rank-order
    Phi
    Tetrachoric

    Biserial
    Gamma

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