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From: peter@entropy.UUCP
Newsgroups: sci.math,sci.physics,sci.crypt,sci.math.stat
Subject: Re: Do you use RANDOM NUMBERS?
Message-ID: <555@entropy.ms.washington.edu>
Date: Sat, 21-Mar-87 12:30:14 EST
Article-I.D.: entropy.555
Posted: Sat Mar 21 12:30:14 1987
Date-Received: Sun, 22-Mar-87 17:34:56 EST
References: <5712@reed.UUCP> <419@esl.UUCP> <2156@pur-phy.UUCP>
Organization: UW MathStat, Seattle
Lines: 17
Xref: utgpu sci.math:730 sci.physics:933 sci.crypt:250 sci.math.stat:75
Summary: Unpredictable need not be random

In article <2156@pur-phy.UUCP>, piner@pur-phy.UUCP writes:
> Just a point of information. It is possible to get a real random
> number from a computer. On Z-80 machines (like the TRS-80) it is
> possible to read the memory refresh register. The register can
> have any value between 0 and 64k. The "RANDOMIZE" function in
> BASIC uses this register to start a psuedo-random number sequence.
> Since the time you select to look at the register is random,
> the number read is random. 

In order to get useful random numbers they have to be independent (in the
sense of probability theory) and uniformly distributed. The fact that the
register can take on any value between 0 and 64k, and you don't know
which, doesn't make it a random number, just an unpredictable one. In
statistical applications random numbers are used to evaluate (using Monte
Carlo methods) procedures that are not amenable to mathematical analysis.
There it is important to produce random numbers that have prescribed 
properties, i.e. that can pass tests of uniformity and independence.