ExponentialDistribution

ExponentialDistribution[λ] represents an exponential distribution with rate parameter λ.

Examples

Random samples:

RandomVariate[ExponentialDistribution[1], 5]
(* {0.32, 1.45, 0.78, 0.12, 2.34} *)

Mean is 1/λ:

Mean[ExponentialDistribution[2]]
(* 1/2 *)

Please visit the official Wolfram Language Reference for more details.