Re: Real-Life Random-Number Generator

From: Leroy Quet (qqquet_at_mindspring.com)
Date: 06/14/04 

Date: 14 Jun 2004 14:09:42 -0700

qqquet@mindspring.com (Leroy Quet) wrote in message news:<b4be2fdf.0406121046.7887721a@posting.google.com>...
> This is a 2-part question, really.
>
> The first part (which is why I posted this to rec.puzzles) is to come
> up with a clever and original means, using real life, of generating a
> 'random' sequence of, say, 0's and 1's.
> (Extra points if you have actually used this method before.)
>
> The second part (which is why I posted this to sci.math) is to come up
> with an effective algorithm which takes the possibly
> not-uniformly-distributed inputted sequence from part-1 and outputs
> another basically random sequence with uniform distribution of the
> sequence's possible values (say, 50% 0's, 50 % 1's).
> (I bet that there are many well-known algorithms for inputting a
> sequence with unknown distribution and outputting a basically random
> sequence with uniform distribution of possible values.)
>
> For example,
>
> We might be at a busy street intersection, and we take note of all
> vehicles travelling past a stop-sign.
>
> If a SUV or truck passes by, we get the next term of sequence A is a
> 0.
> If any other kind of vehicle passes by, we get the next term of A is
> 1.
>
> Now, we do not know how many SUVs/trucks are in our town versus
> smaller vehicles. So we need a method of getting closer to 50% 0's,
> 50% 1's in our random sequence.
>
> A simple but imperfect method might be to let the first term of
> sequence B equal the first term of A. For each additional term,
> sequence B's k_th term equals its {k-1}th term if sequence A's k_th
> term is 0.
> If sequence A's k_th term is 1,
> then sequence B's k_th term is 1 minus its {k-1}th term.
>
> I would bet a better method would be to have a predetermined
> pseudo-random sequence C (with uniform distribution of its values). If
> A's k-th term is 0 we let B's k-th term be, say, C(2k). If A's k_th
> term is 1, we let B(k) = C(2k-1).
>
> But I bet there are still better methods.
>
> thanks,
> Leroy Quet

I see from
http://www.random.org/essay.html
(which was a link given in this thread by someone, but that post seems
to have vanished{?})
that the term for what I want to do in part 2 is
"skew correction".

thanks,
Leroy Quet

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