I don't believe that two coins has any bearing on this situation.

We were told there was a 50% chance of something happening, we were told that one scenario had already happened. - a girl.

That still leaves a 50% chance.

Where did this extra coin come from?

Unless you count twins as one child :D

The available combinations given that one child is a girl is Girl-Boy, Girl-Girl, there is no way they can have boy-boy.

Boy-Girl is the same as Girl-Boy as they already have a girl.

Hi CP!
That's why I told Dr Ron, that Woof had the right answer to the wrong question.

Statistics is a wonderful and indispensable tool in making sense of info, provided it is used the way it was meant to be used.
It has aquired a smelly and dubious reputation only because it is has been, and dare I say will be used in the future to prove things to be either true or false, when logic tells you otherwise.
Still let them prove what they want, as long WE use stats the right way!
Cheers

The coins example is no different to the boy/girl problem.
Where you are confused Chrome Prince is that the order IS important.
The sample space is in fact -

Boy/Boy
Boy/Girl
Girl/Boy
Girl/Girl

Where each outcome is a 1/4 or 25% chance of occuring.

So if the order is not spectific there is a 1/4(25%) chance of having 2 Boys, a 1/4(25%) chance of having 2 Girls and a 2/4(50%) chance of having a Boy/Girl (any order).


Now the problem is conditioned on the fact that there is "at least one girl" so the Boy/Boy scenario can be eliminated fom the sample space leaving -

Boy/Girl
Girl/Boy
Girl/Girl

Where each outcome is a 1/3 or 33% chance of occuring. Given that we have already singles out a Girl, we are left with a Boy in 2 out if the 3 possibilities. This leads to the 2/3 Boy and 1/3 Girl which happens to be the correct answer.

The hard part to comprehend is the wording of the question.

CP,

Get your facts right.

Your coin metaphor is wrong.

Woof clearly stated that both of the 2 children were already begat.

You are wrongly suggesting otherwise when you talk about the 2nd flip of a coin.

The next part of the stated problem, involved X - an information provider (not necessarily a parent KV!) who secretly ascertained the gender of one child. Then if that child was not a girl X then checked the gender of the other to see if that one was a girl.

All that X disclosed was that one of those 2 children was a girl.

You don't know how many childrens' relevant details X examined.

X didn't say that the younger was a girl. Nor that the older was a girl.

KV has wrongly assumed that the parents are informing you that one of the children is a girl.

But you are not making assumptions. Instead you have invented a contradictory scenario.

There is no flipping of a 2nd coin. Both coins have already been flipped.

Enough coins have been examined to truthfully disclose whether a head has occurred.

After I figured the problem through I then googled to see whether this was a classic problem.

Got it in one.

http://mathforum.org/dr.math/faq/faq.boy.girl.html

Meanwhile some of you couldn't even do the right thing and check whether you had read the problem correctly in the first place.

Imagine the response you can expect next time you ask a stats related question.

I tried hard to stay away from this. One billion sperm racing down the chute and the leader pulls up and lets the potential boy thru while saying "we have already been to the trough" Hard and fast the sperm has no prior memory etc This is a straight out 50/50 possible outcome.

At this point other factors arise. Most of these are statitical analysis of past results which have no direct bearing on this event. However people read their own interpretations from these results. The ratio of boys to girls is 50/50 and there is one girl already hence there is a 100% chance that this is a boy. Boy/girl and Girl/Girl is still only 50/50 because we are only dealing with the possible outcome so the factual portion (we already have a girl) is deleted leaving whether this one will be a boy or girl. Other factors may sutblely alter the odds ie a history of girls on both sides of the family,This area produces on average 75% girls or this is Amazonia and boys do not survive birth.
The only way to change it from 50/50 is to show that there is a greater proportion of one sex in the sperm count because nobody is going to say thatone sex swims faster than the other.

this is my only comment as i refuse to allow the quality of the forum to deteriorate.

Besides that I wish all a good day

jfc,i was just wondering if you get sea views from the mountain you live on.....

...........cheers....slowman...............

This is indeed the only correct answer. All other answers depend on the answer to this question.

KV

As far as I am concerned the above quote says it all. If there is a 50/50 chance of an event happening then what has happened before hand is irrelevent. JUst because the ratio of boys to girls born is 50/50 dosent mean to say a family cant have 2 girls and another family have 2boys. The ratio still stays the same.

can't wait for the follow up question woof. :)

Spot on DrRon,

I'm not wrong, and I don't understand if we've been told one is a girl already, why others cannot comprehend that Boy-Boy is an invalid combination.

Amazing.

SLOWMAN

Did you know there are forums on the internet that are not gambling related?
Perhaps you could try a Google search using keywords like,
Forum,"bagging people","Low I.Q."

JFC is in fact one of my favourite contributors.
I don't quite understand his mathematics,but it sure sounds impressive.

you have had three weeks to work that joke out moeee and you still dont get???

3 WEEKS?
Have I?
Oh my GOD!

I must change my user name to SLOWMO!
Maybe I don't got a sense of humour like yours.
Maybe it would work better if you were wearing a clown suit or a big red nose,like the DRUNKARDS have?

JFC is a class act, Probably bipolar [I'm an espie: Aspergous syndrome, a mild version of autism] just like the handbrake is [bipolar] but we get on and understand each other. Check out 'wrong planet.com' to understand JFC and yours truly. I'm a long term member !!! :-) We are easily misunderstood. Imagine a zebra in a paddock of horses. Looks like a horse, eats like a horse but there is somthing not quite right..... Get the picture? Of course the zebra is a nice bloke but unsettles the horses no end. He can't help it, it's who he is :-)

only one thing crash, your average tab/racetrack is full of zebras with a couple horses wandering around wondering what the **** is going on

I new it. I am normal after all [stupid child psychologists]. I feel totally comfortable at a race track. It's everyone else outside of the track that is a fruit-loop !!!

amen to that!

Gday Crash

I know exactly where you are coming from... My partner has a 4 yo boy... He is autistic... can hardly put 2 words together without gibbering... But they (the so called experts) tell us he will learn to hide is autism as he gets older..
I feel that is unfair.. imagine having to hide who you really are just to be socially acceptable...

I have done a lot of reading on the subject and I obviously am no expert, but I am beginning to get an understanding of how autistic people operate. I have read many articles written by people who are autistic, and sometimes I think jeez they think a lot like me.. There is black there is white... there is no grey. They use people to their own ends, they respond in the way they that they suspect others would expect them to respond.. That is why on occassions, people with autism do scare the horses, their respones, to US seem inappropriate. Because they don't know the appropriate response (from society's point of view that is) and respond in an unusual way at times.

People who have no close contact with autistic or Aspergous syndrome people, really have no clue as to how they operate, and are unsettled by them.. People with full on Autism can be a handful, but they are not stupid, they are VERY HIGHLY focussed individuals, to the point of being single minded about a subject that interests them... the worst part of full on autism (to my way of thinking) is the apparent lack of ability to truly love.. they may mouth the words, but words are all they are..(I am sure some of us have said I love you to someone to placate them or to geet em into bed.. I know I have )they view that as a silly thing to waste time on.. and it is hard on my partner knowing her son goes through the motions of loving her, but is incapable of it.. it's not his fault, that is the way he is and we accept him for who he is.. we just wish society would....

Some here could be well advised to do the same :)

So, as someone who doesn't know much about autism, let me be a little politically incorrect here and play devils advocate.

How do we know, on a forum such as this, whether someone is single minded because of some medically recognised syndrome or just because they are an obstinate SOB trying to stir people up. (There is more than one person on here who is probably more single minded than is socially acceptable.) And should we treat them differently if we did know?
I like to think I take people for what they are and treat them accordingly. If someone is a pain in the ar se they should be treated as a p.i.t.a. If they are 'normal' treat them in that way because they deserve it, if they have some syndrome - well, how else are they going to learn to fit in?

There, that should win me some friends - not.

KV's alter ego.

Gday Kenny

I guess I take people at their word on matters such as this. If the truth be known there are probably a lot of non diagnosed autistics running around the place. They are very clever at hiding their "disability" for want of a better word. We think of them as not normal whereas they see us. the non autistic as overemotional and bogged down with feelings, feelings that autistics can't get their heads around... They can play act... but that is all that it is.

AS for fitting in? Why should they? They are individuals like the rest of us. They just think and behave a bit oddly at times (according to our norms) and deserve be given a fair go.

Here is a surprise. I agree with most of the above [the rest was a personal value judgment that others may agree with or may not [depending on who you were talking about:-)]. For the rest of it, in the end, we sink or swim unless obviously seriously handicapped and then you won't find them on any forum.

Aspergerger's or Aspie's for short [I have corrected my original typo spelling mistake I was too late to edit] learn coping skills very quickly. Their big problem is difficulty learning anything they are not especially interested in. In other words, general learning problems even though they often are highly intelligent. Sounds illogical but heck, 'illogical' describes half of life and half of human history.

Espies are at the small end of Autism spectrum disorders and believe me, Wrong Planet Net.com is full of troubled youth more than genuine espie's. There there too, but mostly are the older members. Easy for me to spot the difference in a second. Autism wasn't even known about until not that long ago. I wasn't diagnosed with asperger's until 10 years ago and only after a slip-up from my mother's sister about visits to a Collins st. child psychologist when I was very young and then through visits to one myself after I had found that out. Explained why I had spent my whole youth as a misunderstood loner and unliked mostly. I was terrified of everyone, I thought [I really did] come from another planet. People, especially kids pick up that something is different, they fear that and people avoid what they fear [kill if it was allowed]. Normal human response.

We are not single minded except in extremely rare cases and they make it into the newspapers or docco's [obsessions with train timetables etc,] but we do tend to get into intense detail [handy for punting] and obsession with any subject or hobby we become interested in [I've had many], to the point that would physically exhaust anyone else while we are just cruising happily along. Can be very disturbing for someone living with you. Unusual traits and skills are par for the course and ditto lack of them. I can't remember numbers or letters unless I write them down, It is not uncommon for me to take up to 5yrs. to remember my phone number, pin. number or rego. number, yet because I went through an obsession with history at one stage, I can quote dates, times, places and obscure facts like a machine in any area of history I was interested in. Weird ah ? Anyone ever noticed how many times I edit some of my posts changing one word here or there? Another weird obsessive trait. Thank heaven there is now an editing time limit !!!

No problems with love [I've been married 3 times through good old fashioned love]. Seriously Autistic [or any other well known disorder] people though are rare as hens teeth and movies make it look far worse than it is. Ditto with docco's. They both portray worst case scenarios because it sells. Anyhow, not the place to say more. My original post about it was after a booze-up. I was horrified when I got up realizing what I had said and that I wouldn't be able to edit it out. There are sites available to anyone interested in Autism futher.

What disturbs me though is it is becoming a bit fashionable to have a 'gifted'
aspie child or to use the fact their kid is just a little f.... brat to claim 'he must be autistic' [and deserves special treatment and 'consideration' ..... puke!]. I'd like those parent to experience the real deal themselves for 24hrs. without the coping skills. See how ****** trendy it is after that !!

Cheers and if anyone treats me with any 'special' consideration now, I will just have to track you down and kill you:-)

XPT

Your post is EXACTLY spot on and how it is for most of us. We hide it and through abnormal ability to concentrate on anything we are interested in, become experts at it. Guess what the first thing is that we [all] become obsessively interested in? Hiding it !!! :-)

I slipped up here because of a booze-up.

PS. the case of your friend's child is a rare case of advanced Autism [not an aspie], who is going to be a burden on the parents for the rest of their life [no fun for the kid either]. A tragedy.

I should clarify something quickly. Where I said: 'the ability to concentrate' [abnormally] ,doesn't mean that anything I get into [abnormally] I always become good at. I don't. Just if I have also a natural talent in that area too.

Punting : average. Painting 5ys. [even though a bit colour blind] Hopeless, Guitar: Ditto for the effort and years. ect. Some great others not so great. not even if I'm hopeless, I still keep going at it like a rabbit and know I'm hopeless, but can't stop until it runs it's course. Sometimes years, sometimes weeks.

The important thing in this exercise was that some people should realise they have gaps in their basic probability skills and try to take steps to remedy them, and thus save themselves fiscal grief.

But you cannot resist playing the fool to dumb down this resource even further.

I wonder how much the management appreciate this when they are trying to use this forum to market intelligent rating systems based on mathematical modelling.

As far as I can see Woof's presentation of a classical probability puzzle is correct.




It is wrong to infer that a parent of the kids told you this.

It is wrong to infer that you were shown a picture of them.

It is also wrong to infer as CP later did, that the firstborn was a girl (or in his argument "a heads").

And it is beneath contempt to try to sabotage a philanthropic effort just because your feathers are ruffled.

As it is wrong for Iomaca to commend both of you in your recalcitrance.

Informing me that he once regularly mentally calculated Harmonic Means does not impress me in the slightest. Aiding and abetting such an orgy of ignorance depresses me considerably.

JFC!
Sadly, I have to inform you that I am not smart enough to calculate the harmonic mean for more than 3 numbers mentally. (I can't keep the results in memory) You must be younger than I thought, otherwise you would know, that there were books of tables for just about anything. We used those to get the numbers.
Disagreeing with someone, does not mean dismissing other's ideas! At least, it should not be.
And please calm down. We are not at war with each other.
All the best to you.

one is too many and a thousand is not enough,perhaps thats why slowmoe does'nt drink.........

I think the chance of it being a boy is 2/3.

GREETINGS
Interesting that a MIND game question, can lead to such an opening of HEARTS.

It's obvious that WOOF is not much of a "punter" because he's ----

ASKED A -- "QUINELLA QUESTION" & EXPECTED AN -- "EXACTA ANSWER"