# Poisson Distribution using probabilities

#### Ipsita Bhattacharya

##### New Member
If X follows a poisson distribution where P(X=1)=0.4,P(X=2)=0.6, what is the value of P(X=0)? How will I solve this question?

#### Englund

##### TS Contributor
I think those probabilities are impossible if X is modeled as a poisson process. But, assuming they are possible: What is the probability of X being non-negative?

#### Ipsita Bhattacharya

##### New Member
Actually the answer is positive. That means the question is somehow incorrect?

#### Englund

##### TS Contributor
The probability of a non-negative result is 1. What should P(X=0) be if P(X=1) + P(X=2) = 1?

#### amilsan

##### New Member
but exp(something) = 0 ? thats not possible ln(0), plus in poisson P(X=0) is the highest value
perhaps with the cumulative P(x=1)=0.4 P(x=2)=0.67 with d=2 but i didnt find the answer to that neither
if that 1 or 2 happen conditionally after 100 tries, so in 100 you will have 1 or 2 (if the event happens) or 0 (99% of time), perhaps that could be a poisson aprox

#### Dason

##### Ambassador to the humans
Actually the answer is positive. That means the question is somehow incorrect?
Either the question is incorrect or you've transferred it to the forum incorrectly.

Side note - I don't understand what amilsan is saying at all.