Sample size throws Mason Plumlee under the bus

The narrative goes like this: Duke center Mason Plumlee - who has been a historically bad free throw shooter in his career - suddenly flipped the switch as a senior and became efficient from the line.  The reason was that he developed a new no-dribble routine at the line, which somehow allowed him to focus and make the freebies. Now, for whatever reason, he's no longer a good free throw shooter. Unfortunately - for Mason Plumlee - this is the type of national narrative that arises from people trying to interpret a too-small sample size. He a) changed his routine, and b) was making shots, so 'a' is the cause of 'b'. But math doesn't work that way. Stepping into the way back machine, Kevin Pelton showed that free throw shooting is more random than other measurable basketball skills. And Ken Pomeroy, using John Henson as an example, demonstrated that big increases for bad free throw shooters are exceptionally rare. Here is a game-by-game breakdown ...