I am having probability difficulties...HELP

Quote:

>How can I simulate customer arrivals, in say a restaurant, using

>a Negative Exponential Distribution (NED) in C?

I'll just give some hints, since this looks like a homework problem.

If the probability of a customer arriving in a given period is

constant, then it is fairly easy to show that the probability that a

customer will arrive after t is

P(t) = (1/T) exp (-t/T)

where T is the mean time before a customer arrives. Thus, in a

simulation, one selects a deviate from this distribution to represent

the time between a given point (say opening time or the arrival of the

previous customer) and the next customer.

To select a deviate t, make the change of variables

t = -T log (Tu)

so that

P(u) = u

Clearly, u is a uniform deviate on (0,1] -- err, I've just had a blank

on the notation, but I mean to exclude 0 and include 1. You can

generate uniform deviates using rand() and RAND_MAX in <stdlib.h>, but

be careful to generate them on (0,1] and not [0,1), and then use log()

in <math.h> to generate a value of t.