[gurps] declining probability

[Max, Dunedin, NZ]

Hi, age roles, and stuff use declinging probability, ie your stat starts 
at x, and after a failure, it becomes x-1, and next x-2, until finally 
it equals x-x, at which stage you are dead, unconciouse, or whatever.

I was woudering if somebody has a table for the progression of how long 
(many rolls) this takes, as I'm not to hot with staticits and the bell 
curve.

for example you have a 10, and after two rolls, I believe you (are 
staticically lickly to ) have a 9, etc.

does anybody have a table...

11 --> 3
10 --> 2
9  --> 1.8

(NB:. above were made up numbers as I don' know the real ones)

So then I could just look at the stat's current value at any point, look 
at the roll interval, and know that (on average) they will hit zero in 
so many rolls.


Thanks in advance for anybody who has one


Cheers


Max.