In a certain year, there were 80 days with measurable snowfall in Denver and 63 days with measurable

In a certain
year, there were 80 days with measurable snowfall in Denver and 63 days with
measurable snowfall in Chicago. A meteorologist computes (80 + 1)∕(365 +
2) = 0.22, (63 + 1)∕(365 + 2) = 0.17, and he proposes to compute a 95%
confidence interval for the difference between the proportions of snowy days in
the two cities as follows: