It is easy to show that "The 332nd Fighter Group never lost a bomber" is not accurate. All one needs to do is show that one or more bombers were shot down while being escorted by them, and this has been done.
However, it is not as easy to prove whether the 332nd Fighter Group was "better than," "worse than," or "about the same as" the "average" fighter group.
On the one hand, let us accept as accurate the statement by Daniel Haulman, PhD, described as "one of the world's leading authorities on the all-African-American Tuskegee Airmen" that "The total number of Tuskegee Airmen-escorted bombers shot down by enemy fighters, by my research, was 27, while the average number lost by each of the other six fighter escort groups in the Fifteenth Air Force was 46."
On the face of it, that statement suggests that the 332nd was nearly twice as good as the average of all other fighter groups. However, a real statistics nerd would want to know how the opportunities of all groups compared. How many total missions did the 332nd fly? How many total bombers were escorted by the 332nd? What do those two numbers look like for the other fighter groups?
Without those comparative numbers, we cannot be absolutely certain that the 332nd actually had a better record, percentagewise, than the other groups.
But having said that, my inclination is to assume that the number of opportunities was similar for all the groups (i.e. the other groups did NOT, on average, escort twice as many bombers as the 332nd did.) And if I am right about that, then the statistical evidence does support the notion that the 332nd did have a better combat record than the average of the other groups, and that is indeed how I view the 332nd. Not perfect, but much better than average.