Suppose that over a 12 week period in the summer of 2017, major accidents will occur at a certain business according to a poisson process having a rate of 2.2 per week. what is the probability that at least 3 major accidents will occur during a specific 2 week period?

With an average of 2.2. accidents per week, over a 12 week period, there will statistically definitely be the occasional week with three accidents, as well as accidents with one. We also could also have weeks with zero and weeks with more than three. I don't think we have enough information to accurately answer the question.