# Special Probability help

• Sep 9th 2007, 11:37 PM
nisoo-1
Special Probability help
Q#1.What probability model is appropriate to describe a situation where 100 misprints are distributed randomly throughout the 100 pages of a book? For this model, what is the probability that a page observed at random will contain at least three misprints?
• Sep 11th 2007, 01:00 AM
nisoo-1
reminder for help
dear Sir,
Thanks
• Sep 11th 2007, 03:37 AM
CaptainBlack
Quote:

Originally Posted by nisoo-1
Q#1.What probability model is appropriate to describe a situation where 100 misprints are distributed randomly throughout the 100 pages of a book? For this model, what is the probability that a page observed at random will contain at least three misprints?

Binomial, choose a page evey misprint has a 1% chance of being on the page
so number of misprints on selected page ~B(100, 0.01).

Now it might be that the Poisson distribution is more convienient, but it is
acting in its capacity of approximation to the Binomial.

RonL
• Sep 11th 2007, 04:59 AM
nisoo-1
My method
Is following method right?
n=100,p=0.01 and q=0.99
P(X=x)=(100Cx)(0.01)^x(0.99)^100-x, x=at least three misprints
These probabilites by means of the Poission approximation, using u=np=(100)(0.01)=1, are
P(X=x)=P(x;1)= 1.e^-1/x!, for at least three misprints.
Now I have the confusion in x value How i can calculate x value that is
at least three misprints?
Note: clear the at least three.
Thanks