# On

**URL:** <https://boards.straightdope.com/t/on/34077>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [September 22, 2000, 12:37am UTC](https://boards.straightdope.com/t/on/34077 "2000-09-22T00:37:11Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![bugg](https://avatars.discourse-cdn.com/v4/letter/b/ecae2f/32.png) [@bugg](https://boards.straightdope.com/u/bugg)\
**Post date:** [September 22, 2000, 12:37am UTC](https://boards.straightdope.com/t/on/34077/1 "2000-09-22T00:37:11Z")

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First off, the article I’m referring to is:  
[http://www.straightdope.com/classics/a3\_189.html](http://www.straightdope.com/classics/a3_189.html)

I disagree with Jordan Drachman’s second scenario.

You only know that one of the two children is a girl. Case 1 and case 3 are therefore identical.

Your only possible outcomes are:

male-female  
male-male  
female-female.

We know that the second outcome is impossible, therefore there is a 1 in 2 chance that the other child is a boy,  
and a 1 in 2 chance that the other child is a girl.

-Dan Papasian

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**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\
**Post date:** [September 22, 2000, 12:47am UTC](https://boards.straightdope.com/t/on/34077/2 "2000-09-22T00:47:30Z")

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You’re making a common mistake Dan. You mention three cases above, but your three cases do not have equal probability!

There are four possible outcomes:  
oldest child = girl, youngest child = boy  
oldest child = boy, youngest child = girl  
oldest child = boy, youngest child = boy  
oldest child = girl, youngest child = girl

So in your case, the male-female combination has probability = 1/2. The other choices have probability 1/4.

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**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\
**Post date:** [September 22, 2000, 8:43pm UTC](https://boards.straightdope.com/t/on/34077/3 "2000-09-22T20:43:23Z")

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Pssst, Arnold, you think this thread should have a better title than “On”?

bugg, you used quotes in the title block, didn’t you?

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**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\
**Post date:** [September 23, 2000, 4:25pm UTC](https://boards.straightdope.com/t/on/34077/4 "2000-09-23T16:25:02Z")

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I’m sure you’re right, Irishman, but the title as it is now has a zen-like simplicity that intrigued me. If our friend bugg asks for a less cryptic title I will be glad to oblige.

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**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\
**Post date:** [September 23, 2000, 6:48pm UTC](https://boards.straightdope.com/t/on/34077/5 "2000-09-23T18:48:39Z")

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Here’s three previous threads that seem to be relevant

[http://boards.straightdope.com/sdmb/showthread.php?threadid=629](http://boards.straightdope.com/sdmb/showthread.php?threadid=629)  
[http://boards.straightdope.com/sdmb/showthread.php?threadid=2095](http://boards.straightdope.com/sdmb/showthread.php?threadid=2095)  
[http://boards.straightdope.com/sdmb/showthread.php?threadid=2982](http://boards.straightdope.com/sdmb/showthread.php?threadid=2982)

And here’s two that might be

[http://boards.straightdope.com/sdmb/showthread.php?threadid=90](http://boards.straightdope.com/sdmb/showthread.php?threadid=90)  
[http://boards.straightdope.com/sdmb/showthread.php?threadid=25727](http://boards.straightdope.com/sdmb/showthread.php?threadid=25727)