The Intersection of Events
Sometimes we are interested in the probability of a combination of events rather than just a simple event. To demonstrate this technique, I will use the following example.
Now that my children are older and living away from home, I cherish those moments when the phone rings and I see one of their numbers appear on my caller ID. Experience has taught me that I can categorize these calls as either “crisis,” involving such things as a computer, a car, an ATM card, or a cell phone; or “noncrisis,” when they call just to see if I’m alive and well enough to help with their next crisis.
The following table, called a contingency table, categorizes the last 50 phone calls by child and type of call.
Contingency Table ...