Theoretical result for the probability to have a result from -7 to 7 in a tiebreak considering that the probability to win(lose) a point is 0.5. Horizontal axis is the difference of points from a given and other players. Positive values mean victories and negative losses

I. Y. Kawashima, R. S. Marques de Carvalho, O. Helene, M. T. Yamashita
In this paper we analyse tiebreak results from some tennis players in order to investigate whether we are able to identify some strategy in this crucial moment of the game. We compared the observed results with a binomial distribution considering that the probabilities of winning or losing a point are equal. Using a χ2 test we found that, excepting some players, the greatest part of the results agrees with our hypothesis that there is no hidden strategy and the points in tiebreaks are merely aleatory.

Read more at http://arxiv.org/pdf/1511.06163v1.pdf