According to Bayes' Rule, the probability that they patient has measles given that he has red spots p(H|E) is

• Proportional to the probability of a patient developing red spots when he has measles, denoted by p(E|H)
• Proportional to the probability of developing measles in general.
• Inversely proportional to the probability of developing red spots in general.

Given this information, If the probability of contracting measles is extremely low in the general population, how will this affect the diagnosis? If this probability kept steadily increasing over the years, how will this affect the diagnosis? Likewise, if this probability kept steadily decreasing over the years, how will this affect the diagnosis? If there are many conditions that are more prevalent than measles, and all lead to the development of red spots, how will this affect p(E), and consequently, how will this affect the diagnosis?