Consider if your question would be better at stats.stackexchange.com. Probability touches upon uncertainty, random phenomena, random numbers, random variables, probability distributions, sampling, combinatorics.
See also https://statistics.stackexchange.com
Probability theory is a branch of mathematics that studies uncertainty and random phenomena. It operates by introducing a sample space (a set), and associating probabilities (numbers between 0 and 1, inclusive) to certain subsets of this set, in a manner that satisfies some sensible axioms. If the sample space can be thought of as the real line, we obtain random variables; if it is a Euclidean space, we obtain random vectors. Random variables and random vectors have associated probability distributions, which can be characterized by probability density functions, cumulative density functions, moments, characteristic or moment generating functions.
Typically, questions with this tag will deal with computing (exactly or approximately) probabilities of certain events (from winning a lottery to server outages), drawing random samples, approximating distributions, etc. There might be an overlap with statistics and/or statistical packages (R, SAS, Stata).
Synonym: probability-theory
