In a good weather year, the number of storms in Poisson distributed with mean 1; in a bad year it is Poisson distributed with mean 3. Suppose that any year’s weather conditions depends on past years only through the previous year’s condition. Suppose that a good year is equally likely to be followed by either a good or a bad year, and that a bad year is twice as likely to be followed by a bad year as by a good year. Suppose that last year – call it year 0 – was a good year.

  1. Find the expected total number of storms in the next two years (that is, in years 1 and 2).
  2. Find the probability there are no storms in year 3.
  3. Find the long-run average number of storms per year

Any ideas?