The boy-girl puzzle

not what are the chances that she has girl boy and not boy girl??

Or indeed “What are the chances she boy girl and not girl boy?”

It does exist the combination is still there but some can’t see that.

i must be one of the blind ones then drac, or maybe you’re looking for something that simply isnt there. if i had been so smug from the start of this thread i’d be looking for a way out of admitting i was in the wrong too.

Thing was at the start you claimed it was 0.66 or 66%.

girl/boy and boy/girl are the same IN THE CONTEXT OF THIS QUESTION. the coins comparison does not work because it distinguishes between left and right which adds another variable. a variable which is not in any way aparrent in the OP.

Sadly they’re not the same combination but never mind.

girl/boy and boy/girl are the same, regardless of the 100 families theory. the fact that 100 families spawn 50% mixed, 25% bb and 25% gg has nothing to do with it. there are still 3 options to choose from and when you take them into the context of the question the other 99 families have absolutely nothing to do with it.

Yes they do – because you don’t know which family you are dealing with and the distribution of those families mean that you are twice as likely to be dealing with a family that has mixed children

Just like in the 4999 girls/1 boy question – the other 4999 matter because they are what gives you the odds.

and by the way i just flipped a coin and it came out 70/30 in favour of tails, even though the odds were 50/50 so that puts your 100 families theory right out the window. when the question says it’s a 50/50 chance it means biologically speaking.

F..k me. That’s just not the way statistics works. It is 50/50 on every flip – that doesn’t mean it will come out exactly 50/50 (otherwise every time you tossed a tail you’d know the next one would be a head).
70/30 is pretty normal variance for such a small sample size – flip it a million times and it will come out a bit closer to 50/50.

“Biologically speaking” the odds aren’t actually 50/50 and many other factors effect the outcome.

Thing was at the start you claimed it was 0.66 or 66%.

yes because i was sure that the chances of it being a boy were higher as she had said she had a girl and i was thinking that that lowered the chances of it being a girl twice. I soon saw sense though

mixed
GG
BB (eliminated)

when you look at it like that it’s really quite simple

It is 50/50 on every flip – that doesn’t mean it will come out exactly 50/50

so why are you using the 100 families theory then?

when you look at it like that it’s really quite simple

But wrong.

The PROBABILITY can be calculated exactly – even if small samples suggest it is something else.

If you throw a Head four times in a row, it doesn’t change the probability – the next throw is still just as likely to come up heads or tails – anything else is the Gambler’s Fallacy.

The 100 families example perfectly follows the exact probabilities because it makes it easier to calculate. I could have given you an example with 18.7 billion families where 9.238 billion have mixed, 4.616 billion have two boy s and so on, but I didn’t think it would help. 🙂

Turn it into percentages from the start if you like: 100% of the families have no children. They spawn. Now 50% have a girl and 50% have a boy.
The ones with one girl spawn, (25% 2Girls, 25% Mixed) and the ones with one boy spawn (25% 2boys, 25% Mixed)

In total we now have:
25% of families have 2 Girls
25% of families have 2 Boys
50% of families have Mixed

Pick one random family and the likelihood of it having Mixed (50%) is twice that of it having 2 Girls (25%).

Smee: There is a 100% probability that a higher that average number of people involved in this thread have the memory of a gold fish and forget what they’ve just said.

Indeed Smee, indeed:

Smee: 50:50 end of. Any other solution is just stupid.

Smee: Odds are 2:1 – which is not the same as a probability of 66%

Smee: 2 possible outcomes 50:50 chance.

Smee: The only idiocy that is going on is people not realising that both solutions are correct…..

GrahamS – are you stalking me?

As someone who uses stats and probability on a daily basis I have read this thread avidly. I came to it once the answer had been agreed several times and so until now have not felt the need to comment.

But I would now like to say Graham S you truly have the patience of a saint!

Or possibly the stubbornness of a donkey 😕

also theres the possibility that out of the cross section of 100 families a certain percentage will have twins/ triplets/ octuplets. Riddle me that one GrahamS

I suggest Bomberman you read the original question in full.

yes Drac i understand the answer now thanks. GrahamS is right but that just makes him a smug git for posting a question that he knew the answer to in the first place.

Ah ok.

Ah bomberman has finally seen the light. Excellent!

Perhaps I am smug git, though I think it would have been a bit sh*t if I’d posted a puzzle that I didn’t know the answer to.

Still at least I didn’t jump up and down calling people cretins and penarses when in fact I was wrong. 😛

(apology accepted by the way)

GrahamS – what is the probability that you are incorrect? 50:50 per chance? 😉

Smee

In this case GrahamS is most definitely 100% correct, there’s no 50:50, or indeed 66.66:33.33 about it 😉

*waves at The Sanity Assassin*