Forum

by **General_Tao** on Sun Apr 29, 2012 2:06 pm

The odds of getting a spoil set with 3 cards is exactly 1/3. The odds of getting a set with 5 cards is 100% of course. Has anyone computed the odds of getting a spoil set with 4 cards? I would guess somewhere around 60%? I'm too lazy to get my stat class notes out from the attic for that (involves binomials)...

by **nippersean** on Sun Apr 29, 2012 2:11 pm

7/9 i think

To not get a set

1)any card
2)any card
3)2/3 of a card
4) 1/3 of a card

2/3*1/3=2/9

by **General_Tao** on Sun Apr 29, 2012 3:05 pm

Nip, that looks correct. I've computed it in another way and got the same result, 7/9 it is. Guess we didn't need binomials for this after all.

by **kylegraves1** on Sun Apr 29, 2012 11:13 pm

7/9 is correct

idk why i have trouble getting them though

by **macbone** on Sun Apr 29, 2012 11:54 pm

Yep, 7/9 is correct.

Here's some analysis:

If you know that the other person has neither joker, the odds he has a set with 3 cards are 33.41%; the odds he has a set if he has 4 cards are 77.80%.

by **betiko** on Mon Apr 30, 2012 5:38 am

macbone wrote:Yep, 7/9 is correct.

Here's some analysis:

If you know that the other person has neither joker, the odds he has a set with 3 cards are 33.41%; the odds he has a set if he has 4 cards are 77.80%.

33,41?? why is that? i would v'e said 33.34%.

also about the 4 cards odds, i disregard the 3 first ones, and i just think of the odds of getting a set before receiving my 4th, which would be 66.66%. But if you look at it as a whole, you are right, 77.78%

by **macbone** on Mon Apr 30, 2012 7:48 am

Whoops, forgot the link: http://www.kent.ac.uk/smsas/personal/od ... aq.htm#3.5

He's evaluating the board game Risk, a world domination game that uses cards instead of spoils, but the principles are the same. =)

by **Lindax** on Mon Apr 30, 2012 10:15 am

kylegraves1 wrote:7/9 is correct

idk why i have trouble getting them though

I second that. It often feels like the chance is 10%, especially when it could make the difference between sweeping the map or not getting another turn. :mrgreen:

Lx

by **Trephining** on Fri Aug 10, 2012 3:26 pm

pr(set, given 3 cards) = 1/3, so
pr(no set, given 3 cards) = 2/3

If you have no set with your 3 cards, then you have 2 cards of one color and 1 card of a second color. Without loss of generality, say you have 2 blue cards and 1 green card. Thus from that point the only way you don't have a set on your 4th card is if you draw another green card, and pr(green card) = 1/3.

So we have the path to no set on 4 cards = pr(no set, given 3 cards) * pr(not making set on 4th card, given started with 3 cards that don't form a set) = 2/3 * 1/3 = 2/9.

Therefore pr(set with 4 cards) = 1 - pr(no set with 4 cards) = 1 - 2/9 = 7/9.

by **geegel** on Fri Aug 10, 2012 5:28 pm

If you consider the generic odds then it is indeed 7/9, if on the other hand the first 3 don't give you a set, the odds for the 4th making a set are 6/9.

by **anonymus** on Sat Aug 11, 2012 2:58 am

macbone wrote:
He's evaluating the board game Risk, a world domination game that uses cards instead of spoils, but the principles are the same. =)

i have to check out this "risk" you talk about..

/ :?:

by **Janomike** on Sun Aug 12, 2012 8:32 am

anonymus wrote:
macbone wrote:
He's evaluating the board game Risk, a world domination game that uses cards instead of spoils, but the principles are the same. =)

i have to check out this "risk" you talk about..

/

If someone had told me earlier about this "Risk" i would not have wasted my time here 8-)

by **TDK** on Tue Aug 14, 2012 11:04 am

Interesting, it certainly doesn't SEEM like 7/9...

And since when do you get to play Risk (the board game) with people from all over the world? It's much more fun this way. Although now that I think about it, I'm much better at beating friends and family members than all-comers. :roll:

by **fadedpsychosis** on Tue Aug 14, 2012 11:31 am

TDK wrote:Interesting, it certainly doesn't SEEM like 7/9...

And since when do you get to play Risk (the board game) with people from all over the world? It's much more fun this way. Although now that I think about it, I'm much better at beating friends and family members than all-comers.

+1

by **Kaskavel** on Wed Aug 15, 2012 11:58 pm

betiko wrote:
macbone wrote:Yep, 7/9 is correct.

Here's some analysis:

If you know that the other person has neither joker, the odds he has a set with 3 cards are 33.41%; the odds he has a set if he has 4 cards are 77.80%.

33,41?? why is that? i would v'e said 33.34%.

also about the 4 cards odds, i disregard the 3 first ones, and i just think of the odds of getting a set before receiving my 4th, which would be 66.66%. But if you look at it as a whole, you are right, 77.78%

He is getting his statistics from board risk analysis, where "colours" are fixed for each country. In CC, it is 1/3 exactly.