Re: What happened to radtard?

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From	Richard Heathfield <rjh@cpax.org.uk>
Newsgroups	comp.programming
Subject	Re: What happened to radtard?
Date	Fri, 31 Jul 2015 10:47:30 +0100
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On 31/07/15 10:26, Chad wrote:
> I haven't seen any recent postings by this e-tard. What happened? Did this foolholio finally get a job?

Let sleeping spammers lie.

In the meantime, I think I'll hijack the thread! :-)

Imagine you work for some kind of counter-intelligence agency. (Oh, that
calls to mind some interesting comp.programming threads!) So
"need-to-know" applies. Your boss dumps a frequency distribution on your
desk. It consists of 256 values, sorted into ascending order. So any
structure that the data might have had has been removed.

"What's this about, boss?" you rightly ask.

"We have a block of data. The bytes in it occur with these frequencies.
(So if you add 'em all up, that's how big the block of data is.) Now,
what we want you to find out is this: is it random crap, or is there a
message in there somewhere?"

"How do you expect me to pull a message out of this lot?"

"I don't. I'm only asking you, IS THERE a message in there? If there
isn't, we won't bother looking at it any further. But if there is...
well, I just want to know. Is there a message, yes or no."

"Is it important?"

"Damn right. I want an answer before you go home."

So you stare at these 256 values, and... what?

What is the best way (or, at least, a reasonably reliable way) to
determine whether the frequency distribution you've been given is the
output of a random process?

People who know what I'm talking about are likely to suggest particular
statistical tools (eg chi-square). Although such responses are welcome,
a detailed explanation in English would be appreciated, especially if
that explanation turns out to be easy to turn into C.

Translation: I've looked around on the Net for such an explanation, and
they're all in Greek (or might as well be).

--
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

Thread

What happened to radtard? Chad <cdalten@gmail.com> - 2015-07-31 02:26 -0700
  Re: What happened to radtard? Richard Heathfield <rjh@cpax.org.uk> - 2015-07-31 10:47 +0100
    Re: What happened to radtard? Paul N <gw7rib@aol.com> - 2015-07-31 04:07 -0700
      Re: What happened to radtard? Richard Heathfield <rjh@cpax.org.uk> - 2015-07-31 12:24 +0100
        Re: What happened to radtard? David Brown <david.brown@hesbynett.no> - 2015-08-05 11:08 +0200
          Re: What happened to radtard? Walter Banks <walter@bytecraft.com> - 2015-08-12 14:03 -0400
        Re: What happened to radtard? Paul N <gw7rib@aol.com> - 2015-08-05 15:29 -0700
      Re: What happened to radtard? leif.roar@dimnakorr.com - 2015-08-06 03:31 -0500
  Re: What happened to radtard? fir <profesor.fir@gmail.com> - 2015-07-31 08:10 -0700
    Re: What happened to radtard? Chad <cdalten@gmail.com> - 2015-07-31 23:05 -0700

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