Entertainment For Lively Minds
Eggstrodinary!
Posted by keefus on 25 July 2010 - 12:50pm.
I bought half a dozen eggs a few days ago. So far I've used 3, and every one had a double yolk. Any odds on them all being double?
I'd be eggstatic if they were.
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Funny you should ask
Dealt with pretty well here:
Via http://understandinguncertainty.org/blog/6?page=1
Yolky dolky
Richard Dawkins deals with this kind of thing - our perception of coincidences - and more in his best book, "Unweaving the Rainbow":
http://www.amazon.co.uk/Unweaving-Rainbow-Science-Delusion-Appetite/dp/0...
The thing is though that
if the stats of putting each egg in the box *were* independent, and if double yolks *were* rare (e.g. 1 in 1000), then the combined odds of 6 in a row would indeed be pretty unusual. So it's not really about his perception of coincidences. It's about how likely a box actually is to contain 6 double yolked eggs.
Keefus' question is sensible, imo. Implicit in it is the question of whether seeing 3 in a row has now made it more or less likely that he'll see a full 6. In "O Level" textbook stats, based on completely independent events, seeing 3 (or even 5) makes no difference to the overall final answer.
In the human world we live in though, other factors are relevant. They don't mean stats is bogus-they mean that it has to be used extremely carefully (c.f. the blog I quoted).
For all the human reasons cited in Prof Spiegelalter's blog I'd agree wqith him that seeing 3 in a row *in this context* may well suggest that the chances of a full box are quite high. My street-smart FPO however reckons that the chances are actually lower than random, because most of the double yolkers have already been nabbed for the special boxes-they should weigh more ? Perhaps K will find he has a box of 5. It was meant to be a box of 6 and failed it's final QC check ;-)
Woah, Nick...
Too much maths - I want out!
(*gives blank Father Dougal expression*)
Fair enough
but Spiegelhalter tells it well-it is after all his job. And unlike Dawkins he is a statistician ...
The yolk delusion
I don't think Spiegelhalter and Dawkins are on opposite ends of any argument here.
Dawkins just gives some examples in life where people think a massive coincidence has occurred (and often attribute it to supernatural forces) when in fact, if all the stats are considered, it's to be expected that such things would sometimes happen, and not as rarely as might be naturally thought.
He doesn't use the double yolk eggs example; one example he does use is the likelihood of two people in a room sharing the same birthday, which is more likely than most people would think. His main point is against psychics who play the odds to exploit people.
OK
I'm sure they aren't ideological opposites. But in the stats context they are actually making different points.
In Dawkins' example the likelihood of 2 people in a room sharing a birthday is about (1/365)*(1/365), assuming independence and that any bday is as likely as any other. In round numbers that's v roughly 1/400 times 1/400, i.e 1 in 160 000, so a small chance but not tiny, in a room of a few hundred people for example.
The odds of 6 eggs in a row being double yolkers, *if* we can assume that any individual one has prob of 1 in a thousand, and *if* they are independent events, is much much smaller (1/1000) to the 6th power. Spiegelhalter's point is that the reason we still actually see them quite often is that both the model we used, of independence, is not at all applicable, *and* the 1 in 1000 is also a dodgy number-whereas it's not so obviously a bad assumption for birthdays, is it ?
Anyway, I'll shut up now.
Dawkins & Spiegelhalter
I'm sure they could discuss it amicably over a nice omelette.
Indeed
cheers
N
Not wishing to fuel the fire
But the chances of two people sharing a birthday are nothing like 1 in 160000.
If you were to pick two people at random, the chances of today being both their birthdays is around the 1 in 160000 you mention.
BUT the chances of them sharing a birthday are nothing like that - it's 1 in 365 (excluding the possibility of February 29). Basically, we KNOW when person #1's birthday is, so the probability of that is 1. Then, the independent event that is person #2's birthday? Well, the probability of that happening on the same day is 1 in 365. Thus 1 * 1/365 = 1/365.
Fine
I was assuming we didn't already know it was person no 1's bday, but if we do e.g. the 2nd person is at person no 1's party then fine, you are right.
Also
It depends on the number of people in the room. Dawkins was talking about the pigeonhole principle, whereby the likelihood of two people sharing the same birthday in a room containing 57 people is 99%. With only 23 people in the room, the likelihood is still 50%.
I'm a dog of little brain but...
he suggests, 'if this were the true chance, we would expect to wait 500 million years before this event occurred.'... but why couldn't today be the day it happened, then for it not to happen for another 500 million years or thereabouts? Or am I a meringue?
it could be today
yes. Same as you could win the pools today.
Eggstroardinary
Have you checked the rest yet?
You used to be able to buy...
...boxes of double yoke eggs, so it's definitely occurred before. Pass an egg in front of a strong light source and you can check...Perhaps you have the product of a bored egg-checker?
Waitrose
as mentioned earlier still do them - we've got a carton on the go now.
Is this eccentric
or a Hens Egg Trick?
worst yolk ever
...
Second worst
Forget the singles...I'm waiting for the double albumen
...preferably on shellac.
(needs work)
I don't who it was but someone
described an egg as a perfectly packaged chicken period, enjoy your double yokers!
'Cept it's not!
This joke has always bugged me, and not just because I enjoy eating eggs! It's a clever line at first sight, I suppose, but it is applying a mammalian concept to an avian species. Chickens lay eggs whether they are fertilised or not, female humans only expel unfertilised eggs, accompanied by the unrequired uterine lining. It's not really the same thing!
4th egg cracked this morning
Another double yolker.
Thanks for the stats links; I haven't got the maths to follow it all but I think I get the gist.
Regarding the "randomness" of the eggs, the box was branded "Very Large Free Range", so I think there's two factors increasing the likelihood - if they're chosen by weight, double yolkers are heavier; and maybe free range hens tend to lay more double yolks?
Anyway, watch this space. I might have an omlette tonight...
5th egg cracked
... another double.
I'm unfeasibly eggcited now.
Full House!
All six now. Is there someone I should notify?