They’re not supposed to be the same thing. You would not expect them to have super high correlations Even if the tests were perfect.
> It's notable that MBTI is fairly correlated with the FFM
Sounds like we agree this statement is false
Well if a correlation value is .7 (squared to .49) then you would expect to guess correctly about 75% of the time with just the univariate relationship (naively assuming that the underlying distribution is 50/50 to begin with, without which we would need to refer to something like a RoC AUC score…).