The difference between your best shot and your worst is your "Median Quality". Improve your worst shot and this will improve your overall level.
The idea
Imagine you have a brilliant forehand crosscourt volley (FCV) and an absolutely terrible backhand front drop (BFD). Opponents will learn this quickly and if they are smart, they will avoid giving you chances to hit FCVs and put you in the front on your backhand a lot, or at least on important points. That FCV is much less effective due to your weak BFD.
What to do on court
Too many players practice their best shots way too much. Nobody likes to look silly on court when playing or practicing, so they avoid their worst shot. About 80% of your practice time (maybe more) should be spent on your weak areas. If you play a player who has the same standard for all shots, they are harder to play against than one with one brilliant and one terrible shot.
