In article <3BAF09BF.1057.32F8FF@localhost>,
J.Russell <[EMAIL PROTECTED]> wrote:
>The requirement for the CLT to hold is that there should be a mean
>and st deviation for the background distribution. This I checked in
>Introduction to the Theory of Statistics by Mood, Graybill and Boes
>For a
Rich Ulrich wrote:
>
> >
> But what if I have a population of numbers that is made up of
> 1 billion draws from a Cauchy distribution? No one has ever
> defined this for me, and I have never tested it, but if you *have*
> a sample in hand, then you *can* compute a standard deviation
> even th
> Joe Galenko wrote:
>
> > Just out of curiousity, I'd like to know what kind of population you could
> > have such that a sample mean with N = 200 wouldn't be approximately
> > Normally distributed. That would have to be a very, very strange
> > distribution indeed.
and Gus Gassmann responded:
zation: University of Pittsburgh
Send reply to: [EMAIL PROTECTED]
Subject: Re: what type of distribution on this sampling
> On Fri, 21 Sep 2001 12:47:33 -0400, Joe Galenko
> <[EMAIL PROTECTED]> wrote:
>
> >
> > The mean of a random sample of si
On Fri, 21 Sep 2001 12:47:33 -0400, Joe Galenko
<[EMAIL PROTECTED]> wrote:
>
> The mean of a random sample of size 81 from a population of size 1 billion
> is going to be Normally distributed regardless of the distribution of the
> overall population (i.e., the 1 billion). Oftentimes the magic
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Joe Galenko
Sent: Friday, September 21, 2001 12:30 PM
To: [EMAIL PROTECTED]
Subject: Re: what type of distribution on this sampling
Just out of curiousity, I'd like to know what kind of populatio
Right, I meant to say _approximately_ Normal. If you're writing it down
mathematically then the sample mean is only Normal if the larger
population is also Normal. But in practice, nothing is ever exactly
Normal anyway, so in that sense it's just a matter of when have you have
enough to get a g
Joe Galenko wrote:
> Just out of curiousity, I'd like to know what kind of population you could
> have such that a sample mean with N = 200 wouldn't be approximately
> Normally distributed. That would have to be a very, very strange
> distribution indeed.
You can construct them easily as Bernou
At 12:47 PM 9/21/01 -0400, Joe Galenko wrote:
>The mean of a random sample of size 81 from a population of size 1 billion
>is going to be Normally distributed regardless of the distribution of the
>overall population (i.e., the 1 billion).
i don't think so .. check out the central limit theorem
Joe Galenko wrote:
> The mean of a random sample of size 81 from a population of size 1 billion
> is going to be Normally distributed regardless of the distribution of the
> overall population (i.e., the 1 billion). Oftentimes the magic number of
> 30 is used to say that the mean will have a Nor
The mean of a random sample of size 81 from a population of size 1 billion
is going to be Normally distributed regardless of the distribution of the
overall population (i.e., the 1 billion). Oftentimes the magic number of
30 is used to say that the mean will have a Normal distribution, although
Not to disagree with Randy Poe completely, but I think we can say something,
especially if we make _some_ assumptions (mainly, that this comes from an intro
class).
"@Home" wrote:
> I am trying to solve a ? which basically gives the following facts:
>
> population of unknown number
> popu std de
normal populations result in normal sampling distributions of means ... if
one considers all possible samples
non normal populations never result in exactly normal sampling
distributions regardless of sample sizes (though to the naked eye you might
not be able to tell the difference)
the cent
Stan,
Thanks for the detailed explanation. I have one follwoup ?. You say,
"If the original population is normally distributed, the sample means
will also be normally distributed. Even if the original population
is skewed, the sample means will still be approximately normally
distributed given s
At 06:28 PM 9/20/01 -0400, Stan Brown wrote:
>None that I know, in a formal sense. If you take 100 random samples
>of size 81, or 100,000 random samples of size 81, your histogram of
>sample means will have the same shape, though the curve will be a
>bit smoother with 100,000 samples.
this is fo
I'm just a journeyman in this area, but I'm going to presume to
answer in hopes that if I make any errors the real gurus will
correct me and the shame will facilitate my learning. :-)
@Home <[EMAIL PROTECTED]> wrote in sci.stat.edu:
>I am trying to solve a ? which basically gives the following
"The sample mean is the average of your actual sample
values. It isn't "obviously" 78 or anything else, though
it might be close to 78. And how did you calculate the standard
error?"
I stand corrected on this point. Thanks.
"Randy Poe" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news
"Is it possible to translate it into a z score without any addtional data."
Followup
If all you have to go on is a standard error for the sample of 3 and a mean
of 75, does that give you any hint how bunched at the mean the population
is? Suppose the std error of the sample was 25 or something?
what about if n is only 15 and the population distribution is heavily
skewed? Isn't there a balancing here. Of course w/81 samples, it is hard to
conceive anything but a normal distrib based on the CLT.
"Edward Dreyer" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]
>
>At 05:48 PM 9/20/2001 +, you wrote:
>>I am trying to solve a ? which basically gives the following facts:
>>
>>population of unknown number
>>popu std dev of 27
>>pop mean of 78
>>sample of size n=81
>>2000 random samples
>>
>>The ? is:
>>
>>what is the sample mean?
>>what is the std error
"@Home" wrote:
>
> I am trying to solve a ? which basically gives the following facts:
>
> population of unknown number
> popu std dev of 27
> pop mean of 78
With what underlying distribution?
> sample of size n=81
> 2000 random samples
>
> The ? is:
>
> what is the sample mean?
> what is th
I am trying to solve a ? which basically gives the following facts:
population of unknown number
popu std dev of 27
pop mean of 78
sample of size n=81
2000 random samples
The ? is:
what is the sample mean?
what is the std error (std dev of sample means)
what shape would the histogram be?
The s
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