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ZenGum · 09-04-2010, 11:39 PM

I have seen this issue before, couched in terms of doctors not understanding the statistics of false positives.

Part of the problem is that the simple statement "false positive rate of 7%" is ambiguous.
It might be takes as:
7% of positive tests are false,
7% of false tests are positive or
7% of tests of negative subjects will falsely show positive.
The third is the correct interpretation but the first is the most common one.

The further point about comparing the likelihood of a false positive with the likelihood of actually having the condition is still valid.

09-04-2010, 11:39 PM	#7
ZenGum Doctor Wtf Join Date: Oct 2007 Location: Badelaide, Baustralia Posts: 12,861	I have seen this issue before, couched in terms of doctors not understanding the statistics of false positives. Part of the problem is that the simple statement "false positive rate of 7%" is ambiguous. It might be takes as: 7% of positive tests are false, 7% of false tests are positive or 7% of tests of negative subjects will falsely show positive. The third is the correct interpretation but the first is the most common one. The further point about comparing the likelihood of a false positive with the likelihood of actually having the condition is still valid. __________________ Shut up and hug. MoreThanPretty, Nov 5, 2008. Just because I'm nominally polite, does not make me a pussy. Sundae Girl. Last edited by ZenGum; 09-04-2010 at 11:40 PM. Reason: Grammar Nazism.