SCOTT SIMON, host:
In 2003, Mohan Srivastava got some scratch-off lottery tickets as a small gift. One was a tic-tac-toe game and it won him three dollars - Canadian. But that winning ticket got him thinking about how a lottery commission makes scratch-off games and controls the number of winners. Weve called Mohan Srivastava. Hes a statistician and is the subject of a profile in the current issue of Wired magazine. He joins us from Toronto.
Thanks for being with us.
Mr. MOHAN SRIVASTAVA (Statistician): You're welcome.
SIMON: So do you still have to hold a job or can you live off of scratch-off lottery tickets?
Mr. SRIVASTAVA: Oh, no. I don't think anyone could live off of scratch lottery tickets. Even back then in 2003 when I had a pretty good trick for reading the cards I realized that my day job was probably the one I should stick with.
SIMON: Tell us some of the math involved.
Mr. SRIVASTAVA: It's just taking a look at the visible information that's printed on the face of the card and doing a little bit of pattern recognition.
SIMON: So it's not like holding the card up to a special light or anything?
Mr. SRIVASTAVA: No. It's just taking a look at the numbers that appeared on the face of the card and replace them with ones and twos and threes that recorded whether they showed up once or twice or three times on the card. And by studying those ones and twos and threes you could figure out if the card was a winner of loser.
SIMON: Did the lottery commission know what you'd done?
Mr. SRIVASTAVA: Once I realized that the cards were in some sense marked in that game I gave them a call. And eventually after a bit of telephone tag I decided to send them 20 tickets that I had separated into winners and losers. I said go ahead and scratch them off. And they did and they realized that they really did need to talk to me.
SIMON: Could somebody break the bank of the Ontario lottery with your system?
Mr. SRIVASTAVA: No. No. Because all that happens - if you can get a higher success rate picking winners than you're getting more winners but other people are buying more losers. The lottery corporation's never going to lose in this.
SIMON: Right. Because they determine the number of winners.
Mr. SRIVASTAVA: Right. They'll sell all of the tickets in the game and they control the prize payout. So all that's happening is that the winnings are shifting to the group of people that're able to read the cards.
SIMON: Yeah. But for one person to be able to take savage advantage of it they'd have to drive from, I don't know, Timmins Bay to Toronto stopping at every tavern.
Mr. SRIVASTAVA: In that game - the tic-tac-toe game - the top prize was $50,000. There were four million tickets in the game and there were only eight $50,000 prizes. So it becomes a needle in a haystack problem. If I had seen those tickets I think I would've known that they were winners and high valued winners. But you might never come across them.
SIMON: Mohan Srivastava, geological statistician in Toronto, thanks so much.
Mr. SRIVASTAVA: I enjoyed it. Thanks so much.
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SIMON: This is NPR News. Transcript provided by NPR, Copyright NPR.