text: The central objects of probability theory are random variables , stochastic processes , and events : mathematical abstractions of non-deterministic events or measured quantities that may either be single occurrences or evolve over time in an apparently random fashion .
simplified: The central objects of probability theory are random variables , stochastic processes , and events : mathematical abstractions of non-deterministic events or measured quantities that may either be single occurrences or happen over time in an apparently random fashion .