Quote:
The recipe is simple: play only those rounds where the expected payback is larger than total amount paid for tickets (including yours, of course).

This is not the correct recepie. It is possible to have a +EV gamble on rollover lotteries. Like any gambling transaction, it is +EV if the payout odds are larger than the odds against winning the payout. The number of tickets sold is not a factor in rollover lotteries because its possible for nobody to win, which was why there was a rollover in the first place. Your odds of winning are 1 in however many combinations of numbers there are.

Your payout is a bit more complex to figure out, because there are payouts in addition to the jackpot in most lottieries.

You will also need to factor in taxes. In powerball, the break-even after paying US federal tax is somewhere around $380M. However, it is possible for more than one person to win, so calculating EV needs to calculate the liklihood that you win, but only win half. (Interestingly, you need to do this in Hi-Low split poker too, like the Omaha/8 we were talking about in the other thread).

Lotteries are high variance games, to put it mildly. While you may have a *theoretical* positive expectation, its unlikely that anyone has a bankroll large enough to handle the downswings.

Jim
Edit: I think Bonzi is referring to the total summation of all the tickets purchased since the last jackpot hit. This never changes your odds of winning, however. As he says later in the post, that is related to the combinations of numbers. In the line I quote at the top of this post, both things being compared are related to the payout, not your odds of winning.