>15 men participated in the study
This is no where near the number of participants that would be needed to make such a broad claim
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Experiments have been conducted this way since forever - just 3 days ago I was reading richard feynman's book where he talks about this issue as well - basically the people who try to run experiment properly take longer and are pushed away and never get published or cited, whereas the poorly conducted experiments which show results aligned with what would make headlines get all the attention.
This is why I take any studies, experiments, trials results with a big grain of salt.