出典:Wikipedia
出典:『Wikipedia』 (2011/04/20 23:33 UTC 版)
In information theory, self-information is a measure of the information content associated with the outcome of a random variable. It is expressed in a unit of information, for example bits, nats, or hartleys, depending on the base of the logarithm used in its calculation. The term self-information is also sometimes used as a synonym of entropy, i.e. the expected value of self-information in the first sense, because I(X;X) = H(X), where I(X;X) is the mutual information of X with itself. These two meanings are not equivalent, and this article covers the first sense only. For the other sense, see entropy.