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View Full Version : Pi Notation Fun.

Hazzy
2008-12-10, 06:27 PM
My Stats teacher was talking about how a group of 23 people have a 50% chance of having at least two people in the group sharing a B-Day(Day and month, not year). I had seen a bit about summation and asked if there was a multiplicative(holy crap is that spelled right?) equivalent and I ended up with this.
http://i36.tinypic.com/s6ktqp.gif
Assuming I didn't already know that it was 23 people, is there an easy way to find x other than churning out every value from 1 onward? :f1:
I scarcely remember reading about a formula or something for Sigma Notation...

I asked a few teachers at school... no real help other than using list n a TI-83. D;

Fiel
2008-12-11, 04:41 PM
They have the entire summation formula over at Wikipedia. Do a search for "Birthday Paradox" to get the formula.

xpimnoob
2009-01-02, 03:17 AM
you know whats more fun? probability of same day and year.

Hazzy
2009-01-02, 10:34 AM
you know whats more fun? probability of same day and year.

But then you have to take into account the portion of the population that's age x.
I doubt there's the same amount of 42 year olds as 52 year olds. :f4: