# Thread: Discrete Probability Distributions - Shoot me now!

1. ## Discrete Probability Distributions - Shoot me now!

Using the Poisson Probability Distribution I have the following:

f(x) = m^x e^-m/x!

where f(x) = the probability of x occurances in an interval

m = expected value or mean number of occurrences in an interval

e = 2.71828

Here is the problem:
During the period of time that a local university takes phone in registrations, calls come in at the rate of one every two minutes.

a. What is the expected number of calls in one hour?
b. What is the probability of three calls in five minutes?
c. What is the probability of no calls in five minutes?

The other problem that is kicking my a*# is the following:

Airline passengers arrive randomly and independently at the passenger-screening facility at a major international airport. The mean arrival rate is 10 passengers per minute.

a. Compute the probability of no arrivals in a one minute period.
b. Compute the probability that three or fewer passengers arrive in a one-minute period.
c. Compute the probability of no arrivals in a 15 second period.
d. Compute the probability of at least one arrival in a 15 second period.

I really appreciate it.

ParillaMaster

2. Phone Calls Problem

a. if they get 1 phone call every 2 minutes, then they'll get 30 calls/hour

b. P(3 calls in 5 minutes)
In 5 minutes, the mean number of calls is 2.5
P(x=3) = (2.5^3 * e^-2.5) / 3!

c. P(0 calls in 5 minutes)
In 5 minutes, the mean number of calls is 2.5
P(x=3) = (2.5^0 * e^-2.5) / 0!

Airline Passengers Problem
P(x) = (m^x * e^-m) / x!
m = 10/minute

a. P(0) = (10^0 * e^-10) / 0!

b. P(3 or fewer) = P(0) + P(1) + P(2) + P(3)

c. If they get 10/minute, then the mean for 15 seconds is 2.5
P(0) = (2.5^0 * e^-2.5) / 0!

3. ## Thx

John,

I see my problem on the phone call problem. I forgot to work with the mean of 2.5 calls.

On the airline problem, I did it exactly as you did, almost. My problem, because of my stupidity was I was putting in ^-x instead of ^-m after the e

You are my Probability Savior!!

ParillaMaster

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