Attack of the Bucolic Plague

The Puzzler

RAY: The real question is if the test comes back positive what is the real probability that you actually have the bucolic plague?

Let's say that where you live there are a million people, and .1 percent, or a thousand people out of a million, have the disease.

If the 999,000 disease-free people are tested, the results will say that one percent of them, or 9,990 have the disease when, in fact, they don't.

TOM: They're misdiagnosed!

RAY: Correct. And of the thousand people who do have the disease, the test results will say that 99 percent of them, or 990 have the disease. So we have a total of 10,980 positive results.

But, we know that out of a million people, only a thousand people really do have the disease. So, the chance that you have Bucolic Plague if you test positive is about one in eleven, or less than 10 percent.

The moral of the story is this: You shouldn't lock yourself in the bathroom, unless you have some really good magazines. Do we have a winner?

TOM: Of course! The winner is Jean Gaska from Shelbyana, Kentucky. For having her answer selected at random from all the correct answers that we got, Jean gets a twenty six dollar gift certificate to the Shameless Commerce Division of, where she can choose from a wide array of fine quality Car Talk junk.

[ Car Talk Puzzler ]

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