may 2005 + poisson question

[audia4]

I am not sure exactly how the question goes. But it had something to do with:
In september to october the number of rainy days follows a poisson distribution with a certain mean that I cannot remember, and the other months also have a poissson distribution with a certain mean.

Find the probability that it rains in july august sept , or something like that. Could someone provide the solution to this question?

Thanks.

[Arnold Kim]

I am not sure exactly how the question goes. But it had something to do with:
In september to october the number of rainy days follows a poisson distribution with a certain mean that I cannot remember, and the other months also have a poissson distribution with a certain mean.

Find the probability that it rains in july august sept , or something like that. Could someone provide the solution to this question?

Thanks.

I don't remember the specifics of the problem, but I think you have to remember that the the total number of rainy days from July to November (I think those were the months) also has poisson distribution, where the mean of the total is the sum of the means for July, August, September, October, and November.

[AndrewH]

I remember this question too. I believe it was testing on the additive property as well. You had to add up the means of the months it was testing and use that as your mean for a poisson distribution.