When my friend will be in a combat thesis troublesome tendencies. You should combat your friend's overconfidence barrier. You can make a little humble request and help him with his cognition barrier or bias. We can request him to think about the other perspective of the situation too.
We can make him understand how things might come in other ways also. We can guide him to pursue the statistics research methodology course from the recognized university or we can say that he can pursue a psychology course too.
You might combat his overconfidence barrier, making him a little more humble in his assessments of his own cognitive prowess; more specifically, you might ask him to consider the opposite point of view—to consider how things might have come out otherwise. You might recommend that he take a college or university course in statistics or the scientific method or that he pursue graduate work in psychology.