i thought that women were more likely to have male offspring the older that they got?? or is that a misnomer?

No, definitely not a misnomer.

but older women are more likely to give birth to baby girls than boys

Try this scenario, we toss a coin, which comes down heads 100 times in a row. what do you want to bet on? Heads or tails?

Well given that the odds are almost exactly 50:50, it doesn’t make any difference. In the example previous outcomes do not affect future ones and are therefore irrelevant.

No, definitely not a misnomer.

Isn’t the gender of a child determined by the sperm and therefore nothing to do with the woman or her age?

It must be 50/50.

I had a similarly daft argument once about the Lottery when I said that the odds of the balls being drawn 1, 2, 3, 4, 5 and then 6 in that order are identical to any other set of numbers.

And back to the original post, I think of rolling a die – the odds of rolling the same number again and again are no greater or smaller as each roll is entirely disaffected by the last.

I don’t see how the odds thing works in this scenario – some men produce far more ‘male’ sperm than female, and vice versa… it’s predetermined by nature, not odds?

Isn’t the gender of a child determined by the sperm

Correct, it isn’t.

j_me – Member
Isn’t the gender of a child determined by the sperm
Correct, it isn’t.
POSTED 13 MINUTES AGO # REPORT-POST

last time I was taught biology it was, any links to disprove?

any links to disprove

No but I will admit when I’m wrong ….. bollox !

<thinks> must google before posting </thinks>

I know this ocnfuses people see this
http://en.wikipedia.org/wiki/Boy_or_Girl_paradox
or
http://mathforum.org/library/drmath/view/55640.html

Knowing the date of the boy changes the odds to 13/27 – cant find a link but trust me
GrahamS really knows this stuff I only know the answers.

this assumes a perfect distribution of males and females [ it is 51 v 49].
The extra information is in no way causal but it does affect the proabilities of certain outcomes.
If you know the previous children are all boys as we do the odds are still 50/50 as all those people with 3 childrens of mixed sexes are removed from our set. If we considered everyone with 4 children only 1 in 16 would have 4 males – I have done ordered stats here BTW. only 1 in 16 will have 3 males and then a girl so the odds of that are 1 in 16 so both have the same odds. However the odds of having 1 female and 3 males [ unordered – 3 males then 1 female so we get 50/50 both outcomes have the same odds
A female anywhere in 4 births is 1 in 4] – ie
f m m m
m f m m
m m f m
m m m f
To some degree it depends how you word the question.
HTH

Let me clear this up (3rd year biology degree so I hope i’m qualified enough to). Females have diploid XX chromosomes so after meiosis the haploid gametes are all X. Males have XY chromosomes so produce X and Y gametes in equal quantity. When the gametes combine there is a 50% chance of XY or XX combination hence 50% chance of male or female. Preceding events can’t affect the chances of this so the OP is wrong.

My mum had 3 boys and then a girl – how crazy is that…! 😉

My mum had 3 boys and then a girl – how crazy is that…

Wow, crazy! So she doesn’t know which of them is the girl’s father?

gonefishin – Member

Well given that the odds are almost exactly 50:50, it doesn’t make any difference. In the example previous outcomes do not affect future ones and are therefore irrelevant.

This is if we are dealing with a true coin, what he is suggesting is if you were in this situation and someone tossed a coin 100 time with 100 heads there are two situations.

1. An unlikely even has occurred and the next toss will be 50% chance head tails.

2. Is there a underlying mechanism as work? Maybe the may you are gambling with has a dodgy coin? So given the previous outcomes this effects the probability of the next outcome.

I’m no banker but it would not surprise me if bayesian probability could cause problems if misused. I expect the black scholes equations use bayesian probability.

chuckles

Right. I’m wrong. I think….

Oh – I was convinced up to that point of the thread that you were trolling.

mastiles_fanylion

It must be 50/50.

I had a similarly daft argument once about the Lottery when I said that the odds of the balls being drawn 1, 2, 3, 4, 5 and then 6 in that order are identical to any other set of numbers.

No they are not…

The chances of 1,2,3,4,5 and 6 being drawn in any order is the same as any other set of numbers, but if you add the fact that order is required as well, then it lengthens the odds quite a bit…

but not if you specify the order of the other set of 6 numbers as well.

Well yes, that should be obvious… but that didn’t seem to be what m_f was trying to say…

No they are not…

The chances of 1,2,3,4,5 and 6 being drawn in any order is the same as any other set of numbers, but if you add the fact that order is required as well, then it lengthens the odds quite a bit…

POSTED 10 HOURS AGO # REPORT-POST
Junkyard – Member
but not if you specify the order of the other set of 6 numbers as well.

POSTED 10 HOURS AGO # REPORT-POST
funkynick – Member
Well yes, that should be obvious… but that didn’t seem to be what m_f was trying to say…

POSTED 10 HOURS AGO # REPORT-POST
The order they come out in is irrelevant – any sequence is as likely to happen as the next. For example, the odds of drawing 2, 4, 3, 1, 6 then 5 is identical to drawing 1, 2, 3, 4, 5 and 6 or, indeed, 21, 45, 32, 12, 3 then 48 (or any other random set of numbers).

The order they come out in is irrelevant – any sequence is as likely to happen as the next.

Yes but Junkyard is correctly saying that the ordered set 1,2,3,4,5,6 is less probable than an unordered set of 6 numbers.

That’s true, but the odds of drawing six consecutive numbers are far less than the odds of drawing six non-consecutive numbers. 😀

Knowing the date of the boy changes the odds to 13/27 – cant find a link but trust me
GrahamS really knows this stuff I only know the answers.

*blush*

The original boy/girl thread in all its glory and despair: http://www.singletrackworld.com/forum/topic/the-boy-girl-puzzle

That’s true, but the odds of drawing six consecutive numbers are far less than the odds of drawing six non-consecutive numbers.

Only if you say ANY six non-consecutive numbers.

If you actually pick six non-consecutive numbers then your lottery odds on those numbers are identical to someone that picked six consecutive numbers.

Having said that, you should NEVER pick 1,2,3,4,5,6 fir the lottery, because if you win you’ll be sharing the jackpot with hundreds of other boring pedants and maths geeks making the same point. 🙂

Having said that, you should NEVER pick 1,2,3,4,5,6 fir the lottery, because if you win you’ll be sharing the jackpot with hundreds of other boring pedants and maths geeks making the same point

Very true 🙂

But any order is as probable as the next – it has to be, there is nothing to influence the order so any order or sequence is equally probable such as drawing all odd numbers going backwards from 49 or all six numbers from 20 to 26 except 24 or the same set of six winning numbers being drawn for six consecutive weeks. It is an entirely random draw so any entirely random set of numbers can be drawn.

Nah m_f, the probability of 1 then 2 then 3 then 4 then 5 then 6 being drawn, in that order, is far far smaller than the probability that 1 to 6 ate drawn in any order.

Nah m_f, the probability of 1 then 2 then 3 then 4 then 5 then 6 being drawn, in that order, is far far smaller than the probability that 1 to 6 ate drawn in any order.

Why? It is a random draw. The draw doesn’t understand the significance of sequential numbers, it just draws balls and each one has a number written on it.

That would be like saying the odds of drawing 2, 4, 1, 6, 3 and 5 are smaller than drawing 6, 2, 4, 3, 5 and 1.

And what are the odds of drawing 1, 2, 3, 4, 6 and 5 compared to 1,2, 43, 4, 5 and 6? Or 6, 5, 4, 3, 2 and 1 for that matter.

Right…

For 1,2,3,4,5,6 in that order:

1/49 x 1/48 x 1/47 x 1/46 x 1/45 x 1/44

For 1 to 6 drawn in any order:

6/49 x 5/48 x 4/47 x 3/46 x 2/45 x 1/44

Yeah?

(that may well be the wrong calculation, I’m on a conference call so my stats mind is on hold. But the point is valid: in order only 1 out of 49 numbers will do; in any order any of the 6 required numbers out of 49 will do)

Put another way, there is only 1 draw that will give you 1 to 6 in order, there are 720 draws that yield 1 to 6 in any order.

But the order isn’t significant. There is no more or less reason why any sequence of number will be drawn over another random series of numbers. There can’t be. Surely?

Or am I being to simplistic in my view.

But would you have just single digit numbers in your line, when the probability of drawing any double-digit number is higher than a single digit number, or does that not matter?

Graham’s correct.

To draw them in order, the first ball has to be a 1, so you’ve a 1/49 chance. If the order doesn’t matter, the first ball can be one of six different balls, so you’ve a 6/49 chance.

But the order isn’t significant

It is if you’re betting on a specific order they come out of the barrel which is what Graham says here

Right…

For 1,2,3,4,5,6 in that order:

For the lottery though they don’t keep the order…

m_f… but order is significant as you said…

odds of the balls being drawn 1, 2, 3, 4, 5 and then 6 in that order

Therefore, the first ball drawn has to be a 1, giving odds of 1/49.

If order wasn’t important, as in the normal lottery draw, then that first ball can be any number from 1 to 6, giving odds of 6/49.

Edit: drat.. beaten to it by miketually…

There is no more or less reason why any sequence of number will be drawn over another random series of numbers.

One sequence (1,2,3,4,5,6) is not more or less likely than another sequence (1,6,2,5,3,4). Correct.

BUT that’s not what you are asking about.

You are trying to compare the probability of drawing one particular sequence (1,2,3,4,5,6 in order) versus drawing any one of the 720 unordered variations of that sequence.

Just think about that first ball: in an order sequence it MUST be 1 otherwise you fail, so the odds of the first ball being right are 1 out of 49. For the unordered sequence the first ball can be 1,2,3,4,5 or 6 and we are still on a winner, so the odds that the first ball being right are 6/49.

Edit: drat.. beaten to it by funkynick…

All this (possibly, although I don’t care if its true it’s fun to speculate) proves that Posh is not very liberal with the goodies here is why:

going back to the biology a minute, the sex is determined by the sperm gamete a male either gives an x sperm or a y sperm.

So this is also interesting:

Studies indicate that the sperm with the X chromosome – or female chromosome – have a longer life span than the male sperm (with the Y chromosome).

Yet the male sperm appear to have a higher motility. Sperm motility is measured in two ways: percentage of sperm exhibiting movement, and the quality – or dynamics – of this movement, which is called the forward progression. Poor motility means the sperm have a difficult time swimming toward the egg. FertilAid for Men is a non-prescription male fertility supplement that has been shown to improve sperm motility.

Hence, “female sperm” exhibit less motility – yet have a longer life span. The “male sperm” exhibit increased motility, but have a shorter life span than the X chromosome sperm.

It is believed that if intercourse takes place closer to ovulation, then the probability is greater that the child will be male, due to the high motility (forward progression) and the decreased life span of the sperm.

This has been socially analysed by some commentators that if you have mostly boys then you likely only have sex when she says its OK, if you have mainly girls you are more likely to have regular sex and not care about when she ovulates.

I have two girls………

This has been socially analysed by some commentators that if you have mostly boys then you likely only have sex when she says its OK, if you have mainly girls you are more likely to have regular sex and not care about when she ovulates.

Apparently, Jews are more likely to have sons, because of the cleanliness laws dictating when during a woman’s cycle they can have sex.

We have an office-theory that fathers using computers a lot increases the chance of having a daughter. Three of us have had 5 daughters between us and no boys.

just hope the poor little sod wasn’t conceived in Stoke on Trent!

or Peckham

We have an office-theory that fathers using computers a lot increases the chance of having a daughter. Three of us have had 5 daughters between us and no boys.

I’m behind a desk all day, have two daughters, so whats the theory then?

I’m behind a desk all day and have 2 boys, what’s the theory then? 🙂

I sit behind a desk all day and have one of each. Perhaps I walk to the brew machine more often than most.

i’m behind a desk all day and have 2 daughters.
doing it doggy greatly increases the chance of conceiving girls.
well, that’s what i told my wife. 😀