Why everybody keep saying this? It’s true only if the group surveyed is closed under the “sexual partnership” relation, which is hardly the case in any study.
Unless the group surveyed is deliberately gerrymandered for that, I doubt that would make for a very large difference. If the difference is 10%, as in this study, I have no trouble believing that, especially considering this (though there probably are other sources of noise); but if someone finds nothing obviously wrong with the studies without a fake lie detector where the difference is a factor of 2, and when the arithmetic argument is pointed out to them they say that maybe the group surveyed wasn’t closed under sexual partnership, I would call that clutching at straws.
Unless the group surveyed is deliberately gerrymandered for that, I doubt that would make for a very large difference. If the difference is 10%, as in this study, I have no trouble believing that, especially considering this (though there probably are other sources of noise); but if someone finds nothing obviously wrong with the studies without a fake lie detector where the difference is a factor of 2, and when the arithmetic argument is pointed out to them they say that maybe the group surveyed wasn’t closed under sexual partnership, I would call that clutching at straws.