Re: [Numpy-discussion] non-standard standard deviation

2009-12-11 Thread Dr. Phillip M. Feldman
Anne Archibald wrote: 2009/11/29 Dr. Phillip M. Feldman pfeld...@verizon.net: All of the statistical packages that I am currently using and have used in the past (Matlab, Minitab, R, S-plus) calculate standard deviation using the sqrt(1/(n-1)) normalization, which gives a result that

Re: [Numpy-discussion] non-standard standard deviation

2009-12-06 Thread Colin J. Williams
On 04-Dec-09 10:54 AM, Bruce Southey wrote: On 12/04/2009 06:18 AM, yogesh karpate wrote: @ Pauli and @ Colin: Sorry for the late reply. I was busy in some other assignments. # As far as normalization by(n) is concerned then its common assumption that

Re: [Numpy-discussion] non-standard standard deviation

2009-12-06 Thread josef . pktd
On Sun, Dec 6, 2009 at 11:01 AM, Colin J. Williams c...@ncf.ca wrote: On 04-Dec-09 10:54 AM, Bruce Southey wrote: On 12/04/2009 06:18 AM, yogesh karpate wrote: @ Pauli and @ Colin:                                   Sorry for the late reply. I was busy in some other assignments. # As far as

Re: [Numpy-discussion] non-standard standard deviation

2009-12-06 Thread Charles R Harris
On Sun, Dec 6, 2009 at 9:21 AM, josef.p...@gmail.com wrote: On Sun, Dec 6, 2009 at 11:01 AM, Colin J. Williams c...@ncf.ca wrote: snip What's the best estimate? That's the main question Estimators differ in their (sample or posterior) distribution, especially bias and variance. Stein

Re: [Numpy-discussion] non-standard standard deviation

2009-12-06 Thread Sturla Molden
Colin J. Williams skrev: When one has a smallish sample size, what give the best estimate of the variance? What do you mean by best estimate? Unbiased? Smallest standard error? In the widely used Analysis of Variance (ANOVA), the degrees of freedom are reduced for each mean estimated,

Re: [Numpy-discussion] non-standard standard deviation

2009-12-06 Thread Bruce Southey
On Sun, Dec 6, 2009 at 11:36 AM, Sturla Molden stu...@molden.no wrote: Colin J. Williams skrev: When one has a smallish sample size, what give the best estimate of the variance? What do you mean by best estimate? Unbiased? Smallest standard error? In the widely used Analysis of Variance

Re: [Numpy-discussion] non-standard standard deviation

2009-12-05 Thread Colin J. Williams
On 04-Dec-09 05:21 AM, Pauli Virtanen wrote: pe, 2009-12-04 kello 11:19 +0100, Chris Colbert kirjoitti: Why cant the divisor constant just be made an optional kwarg that defaults to zero? It already is an optional kwarg that defaults to zero. Cheers, I suggested that 1

Re: [Numpy-discussion] non-standard standard deviation

2009-12-05 Thread Colin J. Williams
On 04-Dec-09 07:18 AM, yogesh karpate wrote: @ Pauli and @ Colin: Sorry for the late reply. I was busy in some other assignments. # As far as normalization by(n) is concerned then its common assumption that the population is normally distributed and

Re: [Numpy-discussion] non-standard standard deviation

2009-12-05 Thread Sturla Molden
Colin J. Williams skrev: suggested that 1 (one) would be a better default but Robert Kern told us that it won't happen. I don't even see the need for this keyword argument, as you can always multiply the variance by n/(n-1) to get what you want. Also, normalization by n gives the ML

Re: [Numpy-discussion] non-standard standard deviation

2009-12-04 Thread Chris Colbert
Why cant the divisor constant just be made an optional kwarg that defaults to zero? It wont break any existing code, and will let everybody that wants the other behavior, to have it. On Thu, Dec 3, 2009 at 1:49 PM, Colin J. Williams c...@ncf.ca wrote: Yogesh, Could you explain the rationale

Re: [Numpy-discussion] non-standard standard deviation

2009-12-04 Thread Pauli Virtanen
pe, 2009-12-04 kello 11:19 +0100, Chris Colbert kirjoitti: Why cant the divisor constant just be made an optional kwarg that defaults to zero? It already is an optional kwarg that defaults to zero. Cheers, -- Pauli Virtanen ___ NumPy-Discussion

Re: [Numpy-discussion] non-standard standard deviation

2009-12-04 Thread Pauli Virtanen
Thu, 03 Dec 2009 11:05:07 +0530, yogesh karpate wrote: The thing is that the normalization by (n-1) is done for the no. of samples 20 or23(Not sure about this no. but sure about the thing that this no isnt greater than 25) and below that we use normalization by n. Regards ~ymk The thing is

Re: [Numpy-discussion] non-standard standard deviation

2009-12-04 Thread yogesh karpate
@ Pauli and @ Colin: Sorry for the late reply. I was busy in some other assignments. # As far as normalization by(n) is concerned then its common assumption that the population is normally distributed and population size is fairly large enough to fit the normal

Re: [Numpy-discussion] non-standard standard deviation

2009-12-04 Thread Bruce Southey
On 12/04/2009 06:18 AM, yogesh karpate wrote: @ Pauli and @ Colin: Sorry for the late reply. I was busy in some other assignments. # As far as normalization by(n) is concerned then its common assumption that the population is normally distributed and

Re: [Numpy-discussion] non-standard standard deviation

2009-12-04 Thread Christopher Barker
This is getting OT, as I'm not making any comment on numpy's implementation, but... yogesh karpate wrote: # As far as normalization by(n) is concerned then its common assumption that the population is normally distributed and population size is fairly large enough to fit the normal

Re: [Numpy-discussion] non-standard standard deviation

2009-12-03 Thread Colin J. Williams
Yogesh, Could you explain the rationale for this choice please? Colin W. On 03-Dec-09 00:35 AM, yogesh karpate wrote: The thing is that the normalization by (n-1) is done for the no. of samples 20 or23(Not sure about this no. but sure about the thing that this no isnt greater than 25) and

Re: [Numpy-discussion] non-standard standard deviation

2009-12-02 Thread yogesh karpate
The thing is that the normalization by (n-1) is done for the no. of samples 20 or23(Not sure about this no. but sure about the thing that this no isnt greater than 25) and below that we use normalization by n. Regards ~ymk ___ NumPy-Discussion mailing

Re: [Numpy-discussion] non-standard standard deviation

2009-11-30 Thread Sturla Molden
Colin J. Williams skrev: Where the distribution of a variate is not known a priori, then I believe that it can be shown that the n-1 divisor provides the best estimate of the variance. Have you ever been shooting with a rifle? What would you rather do: - Hit 9 or 10, with a bias to the

Re: [Numpy-discussion] non-standard standard deviation

2009-11-29 Thread Anne Archibald
2009/11/29 Dr. Phillip M. Feldman pfeld...@verizon.net: All of the statistical packages that I am currently using and have used in the past (Matlab, Minitab, R, S-plus) calculate standard deviation using the sqrt(1/(n-1)) normalization, which gives a result that is unbiased when sampling from

Re: [Numpy-discussion] non-standard standard deviation

2009-11-29 Thread Colin J. Williams
On 29-Nov-09 17:13 PM, Dr. Phillip M. Feldman wrote: All of the statistical packages that I am currently using and have used in the past (Matlab, Minitab, R, S-plus) calculate standard deviation using the sqrt(1/(n-1)) normalization, which gives a result that is unbiased when sampling from a

Re: [Numpy-discussion] non-standard standard deviation

2009-11-29 Thread Robin
On Mon, Nov 30, 2009 at 12:30 AM, Colin J. Williams c...@ncf.ca wrote: On 29-Nov-09 17:13 PM, Dr. Phillip M. Feldman wrote: All of the statistical packages that I am currently using and have used in the past (Matlab, Minitab, R, S-plus) calculate standard deviation using the sqrt(1/(n-1))