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Post by rjpageuk on May 27, 2010 16:00:58 GMT
If I havent scared you off by the topic title already then I think you are ready for the counter intuitive world of some weird probability based problems:
1) I have two children. One of them is a girl. What is the probability I have two girls?
2) I have two children. One is a girl born on a Wednesday. What is the probability I have two girls?
These are well known probability problems so a quick google search will find you the answer but I encourage you all to have a think about them and see if you can answer them yourself.
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Post by trubble on May 27, 2010 16:26:49 GMT
Oi. Page. Stop trying to sneak maths onto the Stub. Everyone, it's maths! He is trying to make us do maths!
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Post by alanseago on May 27, 2010 16:41:22 GMT
1) 50% 2) 50% Unless one is a giraffe.
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Post by Weyland on May 27, 2010 16:44:50 GMT
Oi. Page. Stop trying to sneak maths onto the Stub. Everyone, it's maths! He is trying to make us do maths! What you need, Trubs, is the peace of the cool, cultured, marble halls and bee-loud glades of Photofit, where midnight's all a glimmer, and noon a purple glow, and the evening full of the linnet's wings. Get thee to thy Inbox.
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Post by Alpha Hooligan on May 27, 2010 17:12:03 GMT
Oi. Page. Stop trying to sneak maths onto the Stub. Everyone, it's maths! He is trying to make us do maths! You've gone and upset Trubbs now, Rob...are you satisfyed? You bounder! AH
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Post by everso on May 27, 2010 18:37:28 GMT
I can't like Maths.
Rob can't make me.
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Post by riotgrrl on May 27, 2010 19:16:13 GMT
I'll go with Alan's 50%. Alan seems smart.
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Post by housesparrow on May 27, 2010 21:08:53 GMT
Yup, me too.
A lot easier than trying to find the answer on Google.
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Post by rjpageuk on May 27, 2010 21:48:02 GMT
Yup, me too. A lot easier than trying to find the answer on Google. that isnt how it is supposed to work. You lot are hard work . The answer to neither question is 50% though, even though intuitively it seems like it should be.
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Post by housesparrow on May 27, 2010 21:52:59 GMT
OK...you have one girl. The chances of having another girl is 50%. So why is our answer wrong?
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Post by riotgrrl on May 27, 2010 22:18:56 GMT
OK...you have one girl. The chances of having another girl is 50%. So why is our answer wrong? Actually, is more of one gender not born? Can't remember if it's boys or girls, but one of them is more likely than the other to be born, so it's not a 50-50 split. Maybe there is some biological reason why parents of one gender of child are more or less likely to have children of the different (or same) gender? Maybe it's a biological puzzle and not a maths one?
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Post by everso on May 28, 2010 7:50:47 GMT
Surely it's random.
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Post by everso on May 28, 2010 7:55:19 GMT
I think there's a Radio 4 programme at 1.30 today (can't remember the name of it) that will explain all - if you haven't already googled.
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Post by swl on May 28, 2010 8:16:05 GMT
Where does Wednesday come into this? Are you Wenesday-ist?
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Post by bonbonlarue on May 28, 2010 9:51:45 GMT
Q/
I have 4 children, 2 girls, 2 boys. None of whom were born on a Wednesday.
Calculate the probability of a nervous breakdown.
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Post by alanseago on May 28, 2010 10:15:49 GMT
83% for you, 40% for the boys.
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Post by riotgrrl on May 28, 2010 12:09:19 GMT
Well I did google it, but I don't understand the answer.
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Post by alanseago on May 28, 2010 12:25:17 GMT
Well I did google it, but I don't understand the answer. That is because the thesis is based on the entroprothetical deviant. Much simplified in Bertrand Russell's 'Introduction to Philosophy'.
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Post by rjpageuk on May 28, 2010 13:36:36 GMT
Maybe it's a biological puzzle and not a maths one? Its a maths puzzle not a biological one, so just assume the probability of a random person being male or female is 50%. Anyhow, this has gone on enough so I will explain 1) and maybe someone else can get to the answer for 2) from it. Problem: 1) I have two children. One of them is a girl. What is the probability I have two girls?The best way to visualise this problem is follow these steps: 1) Imagine a room full of families. First of all ask everyone to leave who does not have two children. Therefore everyone left has two children satisfying criteria one. Lets assume 400 people are left. 2) Now ask everyone to leave who does not have at least one daughter. Now all the people with both children boys will leave, and the second criteria is satisfied. Out of the 400 people, 100 will have both boys (400 * 1/2 * 1/2), so 300 people remain. 3) Now count how many people out of the 300 left have two girls (100 do). What is the probability that someone in the 300 people left have two girls? The answer is 1/3.
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Post by alanseago on May 28, 2010 14:13:06 GMT
This is surely a phallacious syllogism. You are correlating the percentage of male and female in the population with the likelihood of a mother having a male or female baby.
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