Question: how to calculate confidence level poisson?
Answer: Normal Approximation: For Poisson, the mean and the variance are both lambda (λ). The standard error is calculated as: sqrt(λ /n) where λ is Poisson mean and n is sample size or total exposure (total person years, total time observed,…) The confidence interval can be calculated as: λ ±z(α/2)*sqrt(λ/n).