<P> The alternative specification is sometimes more convenient than the one given above, and some authors will use it as a standard definition . This alternative specification is not used here . Unfortunately this gives rise to a notational ambiguity . In general, the reader must check which of these two specifications is being used if an author writes "X ~ Exp (λ)", since either the notation in the previous (using λ) or the notation in this section (here, using β to avoid confusion) could be intended . An example of this notational switch: reference uses λ for β . </P> <P> The mean or expected value of an exponentially distributed random variable X with rate parameter λ is given by </P> <Dl> <Dd> E ⁡ (X) = 1 λ = β (\ displaystyle \ operatorname (E) (X) = (\ frac (1) (\ lambda)) = \ beta), see above . </Dd> </Dl> <Dd> E ⁡ (X) = 1 λ = β (\ displaystyle \ operatorname (E) (X) = (\ frac (1) (\ lambda)) = \ beta), see above . </Dd>

How to find the median of an exponential distribution