Question

The American Red Cross was founded in 1881, blood types were first identified in 1901 but the first blood bank in the United States was not established until 1932. The blood type distribution in the U.S. is type A: 40%, type B: 10%, type AB: 4%, type O: 46%. Some of the first large-scale use of blood transfusions was to save the lives of the injured during World War II. At that time errors in matching the donors blood with a recipient were common. Blood typing was part of medical exams and tests performed on new recruits and the results were not always accurate. As part of a study on mortality of service personnel at that time it was found that 6% of inductees with type O blood were typed as having type A; 90% of those with type A were correctly typed; 8% with type B were types as type A; and 12% with type AB were typed as type A. For an individual having type A blood, what is the probability that this is their true blood type?

Answer 1