Problem 2: A stochastic process {N(t), t≥ 0} is called a counting process if N(t) represents
the total number of events that have occured up to time t and must satisfy:
(i) N(t) ≥ 0.
(ii) N(t) is integer valued.
(iii) If s < t, then N(s) ≤ N(t).
(iv) For s < t, N(t) - N(s) equals the number of events that have occurred in the interval
(s,t].
Now the counting process {N(t), t≥ 0} is said to be a Poisson process with rate λ, λ > 0, if
(i) N(0) = 0.
(ii) The process has independent increments.
(iii) The number of events in an interval t is Poisson distributed with mean λt and Vs, t≥ 0
$$P(N(t+s)-N(s)=n)=e^{-\lambda t}\frac{(\lambda t)^n}{n!}$$
Based on the above definitions, now consider a Poisson process and let X₁ denote the time of
first event arrival. Let Xn, n ≥ 1, denotes the time between (n-1)st and nth events. The
sequence {Xn, n ≥ 1} is called sequence of interarrival times. Find the probability distribution
of Xn.