franky172
Posts: 160 Joined: Jan. 2007

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: 11*29/30*28/30 = 0.0978
or, also excluding the case when three happen on the same day: 11*29/30*28/301/30*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!
