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The joint entropy of a set of variables is less than or equal to the sum of the individual entropies of the variables in the set.  This is an example of [[subadditivity]].  This inequality is an equality if and only if <math>X</math> and <math>Y</math> are [[statistically independent]].<ref name=cover1991 />{{rp|30}}

The joint entropy of a set of variables is less than or equal to the sum of the individual entropies of the variables in the set.  This is an example of [[subadditivity]].  This inequality is an equality if and only if <math>X</math> and <math>Y</math> are [[statistically independent]].<ref name=cover1991 />{{rp|30}}

一组变量的联合熵小于或等于该组变量各个熵的总和。这是次可加性的一个例子。即当且仅当<math>X</math>和<math>Y</math>在统计上独立时，该不等式才是等式。<ref name=cover1991 />{{rp|30}}

一组变量的联合熵小于或等于该组变量各个熵的总和，这是次可加性的一个运用实例。即当且仅当<math>X</math>和<math>Y</math>独立统计时，该不等式才是等式。<ref name=cover1991 />{{rp|30}}

:<math>H(X_1,\ldots, X_n) \leq H(X_1) + \ldots + H(X_n)</math>

:<math>H(X_1,\ldots, X_n) \leq H(X_1) + \ldots + H(X_n)</math>

== Relations to other entropy measures 与其他熵测度的关系 ==

== Relations to other entropy measures 与其他熵测度的关系 ==