It's impossible, with any certainty, for an investor to prove that his or her judgement is better than random chance. This is high schools stats.
What I take from this is that this person doesn't have a grasp if high school math or is not being honest.
Also if you listen closely to a lot of investors they'll basically tell you their metric is "can I sell this to a greater fool?". This is why there is so much investment in 'hot' areas when, in reality, those are the areas to stay away from as the unicorn shares are likely already over-priced.
What I take from this is that this person doesn't have a grasp if high school math or is not being honest.
Also if you listen closely to a lot of investors they'll basically tell you their metric is "can I sell this to a greater fool?". This is why there is so much investment in 'hot' areas when, in reality, those are the areas to stay away from as the unicorn shares are likely already over-priced.