In: Statistics and Probability
Suppose that it rains in Spain an average of once every 13 days, and when it does, hurricanes have a 4% chance of happening in Hartford. When it does not rain in Spain, hurricanes have a 2% chance of happening in Hartford. What is the probability that it rains in Spain when hurricanes happen in Hartford?
P(rains in Spain) = 1/13
P(hurricanes in Hartford | rains in Spain) = 0.04
P(hurricanes in Hartford | doesn't rain in Spain) = 0.02
P(hurricanes in Hartford) = P(hurricanes in Hartford | rains in Spain) * P(rains in Spain) + P(hurricanes in Hartford | doesn't rain in Spain) * P(doesn't rain in Spain)
= 0.04 * 1/13 + 0.02 * (1 - 1/13)
= 0.0215
P(rains in Spain | hurricanes in Hartford) = P(hurricanes in Hartford | rains in Spain) * P(rains in Spain) / P(hurricanes in Hartford)
= 0.04 * 1/13 / 0.0215
= 0.1431 (ans)