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Probability is not cumulative

I'm as guilty as the next gamer of switching dice after I've rolled a couple of 20s on the assumption they won't do it again; it's a superstition in the face of overwhelming monsters. But I find the current crop of National Lottery adverts even more irritating than usual when they claim that 'luck builds up'. Luck is blind chance is probability is not cumulative. I ranted about this until sbisson complained to the ASA, who say that "luck is both defined and widely recognised as a perceived rather than a real phenomenon" so no-one could believe 'the luck builds up' is a statement of fact. It can't be true, so it's not misleading. In fact, "one could also take the view that the luck builds up because [in a rollover week] there is normally a larger jackpot. Therefore, if you do win, you will be "luckier" as you will stand a better change of wining more money." So you can't be any luckier, except when you're lucky and then you can be luckier.

Am I the only person who finds this both wooly-minded and plain *wrong*?

ASA online complaints form



( 10 comments — Leave a comment )
20th Jan, 2005 07:46 (UTC)
I am doing the lottery for the first time in my life and have been doing it for several months as part of a syndicate at work. we only enter the roll overs. We know perfectly well there is no more chance of winning on rollovers. The reason we do it is that if we won a share of just a few million then we wouldn't be able to retire :-)

And we are IT people working in a bank!

The idea that the everyday man on the street knows about probability is as ludicrous as expecting very man on the street to be able to do a Maths O'level without preparation.

So yes, I agree, but I haven't seen the adverts you mention so I am not complaining to the ASA.
20th Jan, 2005 07:47 (UTC)
I once tried, and failed, to explain to a girl that no, keeping the same numbers week after week didn't make them any more likely to come up than some other set of numbers. She told me it was like two people looking for a friends in a crowd, that it's better to stand still so your friend will eventually find you instead of you both moving. She couldnt' grasp that the lottery numbers are pure chance and have no purpose like a person searching for someone. I gave up eventually.
20th Jan, 2005 11:48 (UTC)
It doesn't make it any more likely that your numbers will match, although it may make it more likely that you remember them and thus spot a win.

So, for some people it may make it more likely that they win a prize. But yes, that is not the same thing as the numbers matching.

20th Jan, 2005 08:20 (UTC)
People also don't understand that having two lottery numbers in the same draw doesn't mean that it's a 1 in 7m chance, but a 2 in 14m. Ach!
"It could be you. But I really wouldn't hold my breath".

20th Jan, 2005 09:10 (UTC)
"it could be you - duck in case a meteorite is on its way"
20th Jan, 2005 09:12 (UTC)
You forgot to specify "A meteorite that's being ridden by Elvis".
20th Jan, 2005 08:26 (UTC)
It's just deliberately misleading.

A rollover suggests an absence of luck in the previous draw, as no-one won it. So therefore, you've got a lot of people's *bad* luck (a share of the un-won jackpot, which is by definition a share of unlucky people's money) building up.

Luck does not build up, but a winner on a rollover is getting a "good" benefit from other people's bad luck. So it's a question of definition.
20th Jan, 2005 08:35 (UTC)
But your average win can be increased by careful choice of numbers - avoid number which other people will choose (their birthdays, for example) and you will have a lower probability that you will have to share your prize...
20th Jan, 2005 09:06 (UTC)
certainly - but if a rollover encourages more people to enter there will be a wider spread of numbers competing with you as well!
20th Jan, 2005 15:36 (UTC)

Sounds actionable, actually.
( 10 comments — Leave a comment )


full steam ahead
Mary Branscombe
Simon & Mary

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