Monday, July 16, 2018

If you win the second set, are you more likely to win the match tie-break? Interesting tennis league stats

In USTA League tennis, the majority of matches are played with a 3-set format where a match tie-break (first to 10 win by 2) is played in lieu of a full third set.

I've often wondered, and sometimes been asked, if the player/pair winning the second set has a better chance of winning the tie-break because they have the momentum, or if the player/pair winning the first rests up in the second and they come back, or if anything really can happen in a tie-break and it is a toss-up.  Well it is time to do some research and find out!

For this analysis I'm going to look at matches played in 2017 in the 18 & Over leagues and just look at the percentage of time the winner of the first/second set win the tie-break.

First, just looking at all matches played, the data tells us that 49.4 percent of first set winners win the tie-break, while 50.6 percent of second set winners do.  Statistically, this says it is a toss-up, although one might argue a slight bias towards the second set winners.

But what if we slice the data different ways?  First, by gender:

  • Male - 49.1% for first set winners, 50.9% for second set winners
  • Female - 49.%% vs 50.5%

So there is the same general toss-up but perhaps slight bias for the women.

Then by level:
  • 2.5 - 52.9 vs 47.1
  • 3.0 - 49.6 vs 50.4
  • 3.5 - 49.3 vs 50.7
  • 4.0 - 49.1 vs 50.9
  • 4.5 - 49.3 vs 50.7
  • 5.0 - 46.9 vs 53.1

Only at the extremes of 2.5 and 5.0 do we see the data stray from the general averages, and there are far fewer matches at these levels so there is a greater chance for some outlier data the skew things.  But even at these levels, there is not a dramatic advantage to either set winner, although interestingly at 2.5 the second set winner wins the match less often!

I did also look at the data by gender and level but nothing stood out, it was consistent with the above.

So it appears there is certainly not a dramatic advantage to the second set winner in a match tie-break, but perhaps an ever so slight one.  Like they say, anything can happen in a tie-break!

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