Say, you have to choose between two doctors (Anna and Berta). To decide which one is better, you check their success rates. Suppose that they deal with two conditions (Coolities and Dummities). So let’s compare their success rate for each of the two conditions (and the total success rate): This is the proportion of healing (success) of the first doctor, Dr. Anna for each of the two conditions: Coolities: 7 out of 8 patients are healed from Coolities Dummieties: 1 out of 2 patients are healed from Dummities This is the proportion of healing (success) of the first doctor, …