APA Dictionary of Psychology

the situation in which observing one event does not provide any additional information about the occurrence or outcome of another event. For example, the outcome of a coin flip and the Dow Jones Industrial Average are independent events, whereas the temperatures of two consecutive days are not necessarily independent. Formally, two events, A and B, are independent if the probability of event A is the same as the conditional probability of event A given event B, that is, P(A) = P(A|B), or equivalently, P(B) = P(B|A). Compare dependent events.