I'm a bit confused about the lambda value of a Poisson distribution. I know it means the average rate of success for a given interval. I'm confused about what this value exactly means through.
For example, If I have 2.4/100,000 people contracting a disease over a period of two years, what is the lambda value if I'm trying to figure out the probability of at least 5 cases of the disease out of 100,000 in one year? I'm not sure if it would be either 2.4/100,000 or 1.2/100,000 since the original average is over a period of two years. I'm also pondering if lambda could be 2.4 or 1.2 since the question already states a sample of only 100,000.