The Time Between Arrivals at an ATM Machine Follows an Exponential

Multiple Choice

The time between arrivals at an ATM machine follows an exponential distribution with $\theta = 10$ minutes. Find the mean and standard deviation of this distribution.

A) Mean $= 10$ , Standard Deviation $= 10$
B) Mean $= 10$ , Standard Deviation $= 100$
C) Mean $= 3.16$ , Standard Deviation $= 3.16$
D) Mean $= 10$ , Standard Deviation $= 3.16$