From: Olaf Klischat <klischat@...>
Date: 2005-07-16T22:10:53+09:00
Subject: Re: [QUIZ] Sampling (#39)

Ezra Zygmuntowicz <ezra@yakima-herald.com> writes:

> On Jul 15, 2005, at 6:10 AM, James Edward Gray II wrote:
>>>
>>
>> P.S.  Taunting each other with fast time readouts is not a  
>> spoiler.  Feel free!  ;)
>>
>> James Edward Gray II
>>
>>
> ezra:~/Sites ez$ time ./sample.rb 5_000_000 1_000_000_000 >  
> big_sample.txt
>
> real    0m43.838s
> user    0m35.820s
> sys     0m1.360s
> ezra:~/Sites ez$ ls -l big_sample.txt
> -rw-r--r--   1 ez  ez  49444445 Jul 15 10:46 big_sample.txt
> ezra:~/Sites ez$ head big_sample.txt
> 168
> 285
> 566
> 604
> 912
> 1183
> 1335
> 1473
> 1728
> 1919
> ezra:~/Sites ez$ tail big_sample.txt
> 999998155
> 999998313
> 999998484
> 999998680
> 999998825
> 999999151
> 999999330
> 999999465
> 999999621
> 999999877
> ezra:~/Sites ez$

Umm... I'm not sure, but that looks a bit too "equidistant" to be
truly random, doesn't it?

The sample being truly random means that the sample should be a truly
"drawing without putting back" (e.g. lottery) sample, so each possible
sample occurs with equal probability. So a sample like

0
1
2
..
..
..
4999999

should occur with the same probability as any other more "likely" one.

That rules out certain more "obvious" (non-)implementations.