The sum of independent, but not necessary identically distributed, exponential random variables follows hypoexponential distribution. We focus on a particular case when all, but one rate parameters of the exponential variables are identical. this is known as exponentially modified Erlang distribution in molecular biology. We prove a characterization of the exponential distribution, which complements previous characterizations via hypoexponential distribution with all rates different from each other.

翻译：独立但不必同分布的指数随机变量之和服从亚指数分布。我们聚焦于一个特殊情况：所有指数变量的速率参数中除一个外均相同，这在分子生物学中被称为指数修正厄兰分布。我们证明了指数分布的一个特征刻画，该结果补充了先前通过所有速率参数互不相同的亚指数分布所得到的特征刻画。