In
probability theory, an
event is a
set of
outcomes of an
experiment (a
subset of the
sample space) to which a probability is assigned. A single outcome may be an element of many different events, and different events in an experiment are usually not equally likely, since they may include very different groups of outcomes. An event defines a
complementary event, namely the complementary set (the event
not occurring), and together these define a
Bernoulli trial: did the event occur or not?