That still makes no sense. If I want to know whether to do a CT scan, the only relevant fact is the increase in probability (in an absolute sense) of cancer th

That still makes no sense. If I want to know whether to do a CT scan, the only relevant fact is the increase in probability (in an absolute sense) of cancer that it causes. It seems like either you, or the entire field of medicine, is obfuscating this basic fact using some field-specific concepts. EDIT: It seems like you are referring to relative risk (http://en.wikipedia.org/wiki/Relative_risk http://en.wikipedia.org/wiki/Relative_risk). But as I said, there is no reason that relative risk should be considered in this case.