Tennis scoring differs from basketball scoring in two important ways.  First, in tennis, points are grouped into games (and games into sets) and the object is to win games, not points.  If this were the only difference, then it would be analogous to the difference between a popular vote and the electoral college in US Presidential elections.

The other difference is that in basketball the team with the highest score at the (pre-determined) end of the game wins, whereas in tennis winning a game requires a pre-specified number of points and you must win by two.  The important difference here is that in tennis you know which are the decisive points whereas in basketball all points are perfect substitutes.

Then to assess statistically whether tennis’ unique scoring system favors the stronger or weaker player (relative to a cumulative system like basketball) we could do the following. Count the total number of points won by each player in decisive and non-decisive points separately (perhaps dividing the sample first according to who is serving.)  First ask whether the score differential is different for these two scenarios.  One would guess that it is and that the stronger player has a larger advantage in the decisive points. (According to my theory, the reason is that the stronger player can spend less effort on the non-decisive points and still be competitive, thus reserving more effort for the decisive points.) Call this difference-in-differential the decisiveness effect.

Then compare matches pitting two equal-strength players with matches pitting a stronger player against a weaker player.  Ask whether the decisiveness effect is larger when the players are unequally matched.  If so, then that would suggest that grouped scoring accentuates the advantage of the stronger player.

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