The textbook basically says that the general addition rule iswhen A and B are two events in a probability experiment. Theprobability that either one of the events will occur is: P (A or B)= P (A) + P (B) – P (A and B). For example, if you take out asingle card from a pack of cards, what is the probability that thecard is either an ace or spade? Therefore, P(A) = 4/52, P (B) =13/52, and P (A and B) = 1/52. P (A or B) = 4/52 + 13/52 – 1/52. P(A or B) = 4/13. Conditional Probability is the probability of oneevent (A) occurring with a relationship to another event (B). Forexample, in a sample of 40 vehicles, 18 are red, 6 are trucks, and2 are both. Suppose that a randomly selected vehicle is red. Whatis the probability it is a truck? P(truck|red) = P (truck and red)/ P (red). P (truck|red) = 2/40 = 18/40 = 2/18 = 1/9 or .11. So, ifwe must find the probability of an event which will occur giventhat another event has occurred, we will use conditionalprobability. If two events are mutually exclusive (no chance ofthings happening together) and you want to find the probabilitythat an event A or B happens, we will use general additionrule.
\"So we could use the general addition rule in the generalelection (in November elections) and use conditional probability inthe primaries?\"
