[SOLVED] OOOOOOOOOok

[dewey_witt]

So i have some cards i want to be able to predict the odds to the draw. there are 3 diferent variable "Rare, Uncommon, and common."..... the draw will be a random three cards....... I need the chances of pulling 1 Rare, 2 Rares, and 3 Rares...... how?

[btherl]

That is a very vague description.  Are you asking us to decide the probability of drawing rare, uncommon and common cards?

[PHP_PhREEEk]

odds can only be mathematically evaluated when ALL variables are known. If any variable is missing, then odds can only be estimated. Need to know how many cards are in each category for starters..

 

PhREEEk

[dewey_witt]

OK there are 10,000 cards total....... 10% are rare, another 30% are uncommon and The remaining 60% are common.

[btherl]

The chances are

 

1 rare - 8.1% (0.1 * 0.9 * 0.9 * 100)

2 rares - 0.9% (0.1 * 0.1 * 0.9 * 100)

3 rares - 0.1% (0.1 * 0.1 * 0.1 * 100)

 

This assumes you are drawing 3 cards, and you don't care which order you find the rares in.  The basic principle is that the p(A and B) = p(A) * p(B), with probabilities expressed as ratios.  0.9 is the probability of NOT finding a rare in any single draw.

[GingerRobot]

Actually, the percentages you gave are for if you DO care which order they come in. If you choose 3 cards, the probability of any one of them being rare is 24.3%:

 

0.1*0.9*0.9 (rare, not rare, not rare)+

0.9*0.1*0.9 (not rare, rare, not rare)+

0.9*0.9*.0.1 (not rare, not rare, rare)

 

=0.243*100 = 24.3%

 

Or in terms of a binomial probability:

 

3 nCr 1 * 0.1^1 * 0.9^2 = 0.243 *100 = 24.3%

 

Anywho, dewey:witt: we need exactly what you want to find the probabiliy of before we can give you a proper answer

[dewey_witt]

You both were a great help tyvm This first is what i was looking for, but the second gave me more idea's. So thanks guys