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franky172



Posts: 158
Joined: Jan. 2007

(Permalink) Posted: Feb. 15 2007,15:53   

Quote (steve_h @ Feb. 15 2007,15:30)
Quote (franky172 @ Feb. 15 2007,15:08)
So the odds of any 2 happening on a specified day are:

(3,2) 1/30*1/30*29/30 or about 0.32 %

The odds of any two happening on any day are:

(2,1) 1/30*29/30, or about 6%.

That's assuming my rusty combinatorics are still correct...

I get a different result (9.8%) for the second calculation by using 1 - odds of all happening on different days.  However, my combinatorics never reached the dizzying height of 'rusty', so I could be wrong.

A quick simulation showed that your result is correct.

The odds of any two happening on the same day are approximately:
1-1*29/30*28/30 = 0.0978

or, also excluding the case when three happen on the same day:
1-1*29/30*28/30-1/30*1/30 = 0.0967

which is also:
(3,2)*1/30*29/30   (because there are three ways to acheive this, any one mass murder could be the 29/30)

<b>not</b>
(2,1)*1/30*29/30  

which I originally had.  Thanks!

  
  29999 replies since Jan. 16 2006,11:43 < Next Oldest | Next Newest >  

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