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 Cauchy
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
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
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 Normal
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 Bernoulli
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
-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 population you
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 dev of
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]...
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:[EMAIL
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
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 for
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
@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 the std error
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 (std dev of sample
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