From: Daryl Lonnon <dlonnon@f...>
Date: Mon, 24 Oct 2005 14:39:49 -0600
Subject: [GZG] Re: laser classes
I respectfully disagree. Tell you what, we each roll some dice 10,000 times (rerolling 6's). I'll roll mine in chunks of 4, you'll roll yours as individuals (so I'm only going to roll 2,500 times). Everytime we roll EXACTLY 4 6's, we pay the other guy a dollar. I'll guarantee you I'll end up on top. Everytime we do it, I'll end up paying you about 50 dollars, you'll end up paying me about 300. The mistake you're making is that you're assuming independence between dice rolls. There IS dependence between set of rolls (within a set of rolls it's independent). Where I'm defining a set as a fistful of dice (4 in this case versus 1). The dependence between sets of rolls is that you don't get to roll that dice again if you don't roll a 6! Or to use your example from below (hopefully I get all the numbers correct): Probability of rolling EXACTLY 4 6's when rerolling 6's (everthing in a parathensis can be viewed as one "roll (of potentially multiple dice)") 1 dice: 1st 2nd 3rd 4th 5th (1/6) * (1/6) * (1/6) * (1/6) * (5/6) = 0.00064 2 dice: (1/6 * 1/6) * (1/6 * 1/6) * (5/6 * 5/6) + (1/6 * 1/6) * 2(1/6 * 5/6) * (1/6) * (5/6) + 2(1/6 * 5/6) * (1/6) * (1/6) * (1/6) * (5/6) = 5 * (1/6)^4 * (5/6)^2 = 0.002679 3 dice (1/6 * 1/6 * 1/6) * 3 (5/6 * 5/6 * 1/6) * (5/6) + 3 (1/6 * 1/6 * 5/6) * (1/6 * 1/6) * (5/6 * 5/6) + 3 (1/6 * 1/6 * 5/6) * 2 (1/6 * 5/6) * (1/6) * (5/6) 3 (1/6 * 5/6 * 5/6) * (1/6) * (1/6) * (1/6) * (5/6) = 20 * (1/6)^4 * (5/6)^3 = 0.0089 4 dice (1/6 * 1/6 * 1/6 * 1/6) * (5/6 * 5/6 * 5/6 * 5/6) + 4 (1/6 * 1/6 * 1/6 * 5/6) * 3 (1/6 * 5/6 * 5/6) * 5/6 + 6 (1/6 * 1/6 * 5/6 * 5/6) * (1/6 * 1/6) * (5/6 * 5/6) + 6 (1/6 * 1/6 * 5/6 * 5/6) * 2 (1/6 * 5/6) * (1/6) * (5/6) + 4 (1/6 * 5/6 * 5/6 * 5/6) * (1/6) * (1/6) * (1/6) * (5/6) = 35 * (1/6)^4 * (5/6)^4 = 0.013 Hopefully this makes some sense, Daryl > On 10/24/05, B Lin <lin@rxkinetix.com> wrote: For > a total of 2 in 18 or 1 in 9. gzg-l-bounces+tom.mccarthy=xwave.com@lists.csua.berkeley.edu > ]