Infinite probabillities

[Chrisz]

Well.. I'm trying to create a type of infinite probabillity, in which say... lets use basketball as an example, a player can be good, but no one, can ever, score ALL the baskets they take. Begginners will be able to score some baskets, 1 in 10 chance say, Amateurs will be able to score say 6 in 10, and Pros, say 9 in 10, but no matter how good they will get they won't ever score 10 in 10.. (Though some people will but, just imagine they cant ;D)

At first to tackle this I thought, half lives!

e.g...

10, 5, 2.5, 1.25, 0.625..... etc etc.. Always halves the number, but never reaches 0... That is great and all.. But i cant think how to apply this to my problem. x.x And besides the leap from level 1, 10, to level 2, 5, thats huge. :X Thats a whole 5 units :O. Yeah.

NPC Code:

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chance = random(1,10);

if (chance == ?) {

  //...

}

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What would ? be substituted for, even if half lives were used to calculate the probabillity?.. It's confusing. ! I either need help with this, or a brand new concept. x.x