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The question I have is how to test if two proportions from the same sample of patients are significantly different from each other, indicated by a p-value?

Example: 100 people, 1 has Disease A and 2 have Disease B. Is the occurrence of Disease A more frequent than Disease B, ie. occurrence of Disease A given by 1/100 compared to 2/100 for B?

Keyword is 'same' sample of patients. Any help would be much appreciated. :)

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Can the same patient have both diseases? – Michael Chernick Aug 16 '12 at 11:24
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Since these samples are the same standard inference assuming independent random samples form a given population is violated. What is the inference that you want to make? Are you wanting to test whether or not the data indicate that the incidence for B is greater than for A in the population that the 100 patients were sampled from? – Michael Chernick Aug 16 '12 at 11:32
@Michael Chernick: yes patient can have both diseases.I do want to test whether or not the data indicate that the incidence for B is greater than for A in the population that the 100 patients were sampled from – bioinformant Aug 16 '12 at 11:42

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up vote 2 down vote accepted

What you're asking about is a test of dependent (or paired) proportions. Please see this article on McNemar's test or this calculator site (its language isn't the clearest, but it will help you calculate the result you're looking for).

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