1. The problem statement, all variables and given/known data What kind of equations you'll get when trying to find confidence limits 100(1-a) % for λ in Poisson distribution? 2. Relevant equations Poisson distribution P(X=x) = e-λ λx / x! (x=0,1,2 .....) 3. The attempt at a solution I made an equation as follows: Ʃ (k = from k0 to n) e-λ λk / k! = a/2 to solve the confidence limits. Am I doing correct thing here? I cannot solve λ from that equation + I'm not supposed to have infinite sums in my equations... Any help for me?