[metapost] Drawing a urn

[Troy Henderson]

Martin,

Try replacing

>      if (i <= 5 ):

with

       if (normaldeviate <= 0.176374 ):

If I understand your problem correctly, this should solve both of your
questions.  The reason for choosing 0.176374 is because normaldeviate
is a normally distributed (pseudo) random number whose mean is 0 and
whose standard deviation is 1, and the probability that such a number
is <= 0.176374 is 0.57.  Obviously, you would want to change that
value if you decide to change your probability.

-- 
Troy Henderson
Assistant Professor
Department of Mathematics
University of Mobile
http://www.tlhiv.org