Re: Random Number Generator Problem
From: Jim Gordon MVP (goldkey74_at_WarmerThanwarmMail.com)
Date: 12/06/04
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Date: Sun, 05 Dec 2004 20:37:13 -0500
Hi,
The random number feature in Excel 2004 works differently from all other
versions of Excel. There's a detailed explanation of this somewhere in
Microsoft's support site, but at the moment I can't find that information
for you.
I'll keep looking.
-Jim Gordon
Mac MVP
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----------
In article <jemcgimpsey-DFAA8E.10342405122004@msnews.microsoft.com>, JE
McGimpsey <jemcgimpsey@mvps.org> wrote:
>
> In article <694ea65e.0412042110.3d3998d3@posting.google.com>,
> christopherpeck1971a@yahoo.com (Chris Peck) wrote:
>
>> Please tell me if I am doing something stupid, but I having trouble
>> generating random numbers. If I select Tools: Data Analysis: Random
>> Number Generator, then select Normal Distribution, Mean 0, Standard
>> Deviation 1, and then I select my range of output, I get the SAME
>> numbers everytime!!! What's worse, the top left number is 9.XXX
>> (considering the mean is 0 and standard deviation is 1, that is pretty
>> much impossible).
>>
>> I am using Excel 2004 (Mac)
>
> All common RNGs are really pseudo-random-number-generators, using
> functions that (in theory) don't repeat values for a very large number
> of iterations. However, if you feed the same number into the RNG's
> function, it will always produce the same result.
>
> Each operation of the ATP's RNG has an optional parameter that allows
> you to start the function at the same point, and thus get the same
> values time and again. It's called the Random Number Seed. If you clear
> that box, the generator will use a different seed every time (probably
> based on the internal clock.
>
> See "Options in the Random Number Generation dialog box" in XL Help.
>
> Note, however, that for serious statistical work, the ATP RNG is pretty
> lousy, generating repeated numbers and mediocre distributions.
>
> Look in the excel groups archives:
>
> http://groups.google.com/advanced_group_search?q=group:*excel*
>
> for posts on generating normal distributions. For discussion on the
> inadequacies of XL's various RNGs (i.e., ATP, RAND(), VBA's Rnd()), look
> for posts by David Braden and Jerry Lewis, among others.
>
> FWIW, XL04's RAND() appears to be much improved over previous versions.
> ATP's RNG and RANDBETWEEN() aren't.
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