False Positive Puzzler

RAY: Let's say if it was 100 people who took it . . . let's start here, Tommy, 100 people.

TOM: No, I'm with you. I was on a different track. I'm with you. Fifty people who take the test will test positive and yet they will not have it.

RAY: Right. So out of 1,000 people who take it . . .

TOM: Yeah.

RAY: OK? And you're included in that thousand.

TOM: Yes.

RAY: OK? Fifty-one people out of 1,000 are going to test positive. One of those people is going to have it and 50 are not going to have it.

TOM: Correct.

RAY: So your chances of actually having it, even though you tested positive, are one in 51, or a little less than 2 percent.

TOM: Two percent.

RAY: And that's just another way that statistics can fool and lie to you and make you jump, suicidal . . . and jump off a bridge because you tested positive.

TOM: Sure.

RAY: And the test is 95 percent accurate.

TOM: It sounds so good. So you're saying 2 percent is pretty small.

RAY: Well, I mean, your chances of having it are twentyfold greater than just a person off the street.

TOM: Exactly. Right.

RAY: You know?

TOM: Which is only .1 percent.

RAY: By testing positive.

TOM: Yeah.

RAY: But it's still . . . I mean, considering how dire the news was just a moment ago . . .

TOM: It's now down to 2 percent.

RAY: It's down to 2 percent. I mean . . .

TOM: Don't even pay any attention to it.

RAY: You've got a 2 percent chance of being hit by Skylab. Is that still up there? Anyway, who's our winner?

TOM: The winner is . . . no kidding.

RAY: Jeez.

TOM: What are the chances of this? Wow. The winner is a guy named‹and I'm going to pronounce it correctly for us‹Frank Maggliozi, or, as some people would say, Maggliozi from Rye Brook, New York. Wow.

[ Car Talk Puzzler ]