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Thread: Sample size

  1. #1
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    Sample size

    Hi I'm trying to work out how a previous study calculated their sample size. They're are looking at two different diagnostic test and performing both test on the same patient before using x-ray as a reference tool.

    They say: A 15% difference in specificity was considered clinically significant. Power analysis was aimed at enabling the detection of a 15% difference in specificity between the two test using a power of 80% (2 sided, alpha = 0.5). This resulted in a minimum of 87 participants to be included in the study.

    Not sure what formulae they have used.

    Let me know if anymore info is required, link to paper here.

    Thank you in advance.

  2. #2
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    Re: Sample size

    they say in the article that they used a chi-squared test and presumably Cohen's Kappa. For both, the formula is easily accessible with google.


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