2.II.12F
Part IA, 2005
Let be a ranking of the yearly rainfalls in Cambridge over the next years: assume is a random permutation of . Year is called a record year if for all (thus the first year is always a record year). Let if year is a record year and 0 otherwise.
Find the distribution of and show that are independent and calculate the mean and variance of the number of record years in the next years.
Find the probability that the second record year occurs at year . What is the expected number of years until the second record year occurs?