"Why did these all fail to reject the null hypothesis. That's a powerful question." Because that's nearly always the outcome. By conventional statistical metri

"Why did these all fail to reject the null hypothesis. That's a powerful question." Because that's nearly always the outcome. By conventional statistical metrics, the null hypothesis isn't rejected >=95% of the time. "The studies saying the five can't be reproduced, where are they." They don't get published, because of the aforementioned statistical problem. The bias toward positive results isn't irrational; it's a natural response to the fact that the vast majority of what any scientist produces will be a "negative" result. The way you learn what not to try is by studying under experienced scientists, and talking to other current practitioners. For any field, there's a vast shared experience that guides experimentation. As a new researcher, a good place to find this kind of information is in review articles and book chapters. But mostly you get it by working with experienced people.