Probability

As the Twelfth Doctor described, probability was a branch of mathematics that gauged the likelihood of future events which could not be predicted with absolute certainty. (COMIC: Gangland)

The Time Lords could create a fixed point in time by using their abilities to freeze a probability into a certainty. (PROSE: The Gallifrey Chronicles)

The unusual properties of Tick-Tock World could create multiple equally probable occurrences of a single event. When the First Doctor was devoured by a Xesto, he awoke in a hinterland populated by several alternate versions of himself, which a future version of Susan Foreman explained were the victims of equally probable, but slightly different, ways that he could have endured such a fate. (AUDIO: Tick-Tock World)

The computer of a Chula warship estimated a 100% probability that any attempt to jettison a German bomb would precipitate detonation, and that Captain Jack Harkness would be terminated in under two minutes. However, Jack was ultimately retrieved by the Ninth Doctor. (TV: The Doctor Dances)

When in Las Vegas, the Twelfth Doctor explained to Clara Oswald that rigorous probability calculations governed his actions, demonstrating this by using his mathematical skills to win at gambling. (COMIC: Gangland)