Only fighters with 10+ UFC fights have been included (otherwise Khamzat would sit at the top - he takes almost no damage and wins a lot… - and it would shock people)
The ranking is done by aggregating data ranging from wins/losses/draws to fight statistics (accuracy in striking, takedowns and their corresponding defense), fights durations and fight counts. The resulting number is then gaussian-normalized to reflect the distribution of the original IQ.
A higher number = better ; my personal interpretation is that regardless of stylistic considerations, a fighter who manages to win his fights in a minimal amount of time, with maximum accuracy and minimal damage to himself de facto demonstrate a high Fight IQ.