What is probability for a family to have all their 3 children to be male?

[waqar1155]

suppose the probability of having a male and female child is same?
A)50% B)37.5% C)25% D)12.5% E)less than 10% what is answer

[bednobs]

it's 50% isn't it?

[kawakiri]

25%

[kawakiri]

http://www.in-gender....Odds/Gender_Odds.aspx

[kawakiri]

At the onset before any children I would say the likelihood of 3 boys would be 25% however if we know there are already two the likelihood of the next child is still 50/50 however according to the link above 51/49 in favour of a boy.

[Calibax]

c) 12.5%
prob of 1st child being male = .5
prob of 2nd child being male = .5
prob of 3rd child being male = .5
so prob of all 3 being male is .5 x .5 x .5 = .125 = 12.5%

[Buenchico]

Year 9 Maths homework perhaps?

P(All same) = P(all boys) + P (all girls)
= (0.5 x 0.5 x 0.5) + (0.5 x 0.5 x 0.5)
= 0.25

[factor-fiction]

It depends on what you are asking. If you are starting from scratch the probability of the first child being a boy is 50/50= 50% = 0.5 = ½
The probability that thesecond is then a boy is a half making the total probability of a both being boys to be ¼ (25% or 0.25)
Then the chance of the third being a boy is again ½, and the proability of all 3 being boys is ½ x ½ x ½ = 1/8

But if your starting point is "I have had a boy, what is the probability that my next two are boys" then the answer is
½ x ½ = ¼

[Buenchico]

Aaagh!
I really must learn to read questions properly!
I saw it as requiring that all three children should share the same gender, rather than all be male.

So, as Calibax states (and as is included within my answer above):
p(B, B, B) = 0.5 x 0.5 x 0.5 = 0.125

[Buenchico]

Factor 30 is, of course, also correct.

However Factor30's second paragraph refers to a 'conditional' probability which is not implied by the question.

[society]

My mum had six girls then two boys. If she had a ninth child would it be a boy? Do you think?

[factor-fiction]

Hi Chris, if it's homework I'm sure the correct answer is 1/8 = 0.125 a steh stated question doesn't imply conditional probability.
I was just making the point that if the questioner has had 3 children, all boys, and thinks that's an amazing coincidence then in reality it's not that unusual an outcome- maybe she'd have asked the same question if she'd had 3 girls.

[factor-fiction]

Hi Society (Isn't that a musical?)- no, I'd say there is a 50/50 chance of the next one being a boy (unless there is something in her makeup that makes it more likely she has girls). There's certainly no reason why the 9th child is more likely to be a boy than a girl. The reproductive system has no memory as far as I know.

[dzug2]

My mum had six girls then two boys. If she had a ninth child would it be a boy? Do you think?

50:50 going on the assumptions of this question.

In reality she (or her husband) might have a genetic disposition to produce girls so it might not be that simple.

[society]

Factor, thanks for the response.

From a scientific point of view I knew that but always wondered...

You know what's interesting, all my sisters only have girls and my two brothers have boys.

[factor-fiction]

Yes, my mum had 4 boys yet her sister had 4 girls, but in a population of 60 million all sorts of things that seem highly unusual happen frequently