, filtered cigarettes with unfiltered joints, to claim the marijuana smoke—that is, the unfiltered smoke---is more dangerous, a well known result from comparing filtered
and unfiltered cigarettes; it deals with the method
of smoking and does not compare tobacco and marijuana);
--It enhances the guesses of harm from marijuana smoking by an unrelated factor, concurrent cigarette smoking (whereas controlling for separate variables is essential if science is to obtain meaningful scientific results