Satterthwaite-newbie question

[Allyson Rosen]

I need to compare two means with unequal n's. Hayes (1994) suggests using a
formula by Satterthwaite, 1946.  I'm about to write up the paper and I can't
find the full reference ANYWHERE in the book or in any databases or in my
books.  Is this an obscure test and should I be using another?

Thanks,

Allyson




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ASA and patenting

[T.S. Lim]

Consider the following excerpts from the ASA Ethical Guidelines for Statistical 
Practice (http://www.amstat.org/profession/ethicalstatistics.html). My naive 
interpretation is that the ASA may endorse patenting statistical innovations or making 
them proprietary. What's your interpretation?

===
Make new statistical knowledge widely available, in order to provide
benefits to society at large beyond your own scope of
applications. Statistical methods may be broadly applicable to many
classes of problem or application. (Statistical innovators may well be
entitled to monetary or other rewards for their writings, software, or
research results.)

Make new statistical knowledge widely available in order to benefit
society at large. (Those who have funded the development of new
statistical innovations are entitled to monetary and other rewards for
their resulting products, software, or research results.)
===



--
T.S. Lim
[EMAIL PROTECTED]
www.Recursive-Partitioning.com




Get paid to write review! http://recursive-partitioning.epinions.com




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Re: basic stats question

[Jay Warner]

Richard A. Beldin wrote:

> This is a multi-part message in MIME format.
> --20D27C74B83065021A622DE0
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
> 
> I have long thought that the usual textbook discussion of independence
> is misleading. In the first place, the most common situation where we
> encounter independent random variables is with a cartesian product of
> two independent sample spaces. Example: I toss a die and a coin. I have
> reasonable assumptions about the distributions of events in either case
> and I wish to discuss joint events. I have tried in vain to find natural
> examples of independent random variables in a sample space not
> constructed as a cartesian product.
> 
> I think that introducing the word "independent" as a descriptor of
> sample spaces and then carrying it on to the events in the product space
> is much less likely to generate the confusion due to the common informal
> description "Independent events don't have anything to do with each
> other" and "Mutually exclusive events can't happen together."
> 
> Comments?

1)It is conceivable, that a plant making blue and red 'thingies' on 
the same production line would discover that the probability that the 
next thingie is internally flawed (in the cast portion) is independent 
of the probability that it is blue.

BTW - 'Thingies' are so commonly used by everyone that it is not 
necessary to describe them in detail. :)

2)There are many terms, concepts, and definitions in the 'textbook' 
that have no exact match in reality.  Common expressions include, "There 
is no such thing as random,' 'There is no such thing as Normal 
(distribution),' and my own contribution, "There is no such thing as a 
dichotomy this side of a theological discussion.'  The abstract 
definitions are just that - theoretical ideals.  Down here in the mud of 
reality, we recognize this, and try to decide if the theory is 
reasonably close to what is happening.   A couple confirmation trials 
help, too.

If the internal casting flaws are generated at an early point, and the 
paint is added later, depending on the orders received, then I would 
assert that independence was likely.  If the paint is added to castings 
made on different dies or production machines, as a color code, then I 
would suspect independence was unlikely.

3)Presenting 'independence' as axes in a cartesian coordinate system 
is extremely handy, especially for discussing orthogonal arrays and 
designed experiments, etc.  The presentation, however, does not make 
them independent.  One has to check the physical system behavior to 
assure that.

4)I may have shot far wider than your intended mark, in which case, 
sorry for the interruption.

Jay

-- 
Jay Warner
Principal Scientist
Warner Consulting, Inc.
 North Green Bay Road
Racine, WI 53404-1216
USA

Ph: (262) 634-9100
FAX:(262) 681-1133
email:  [EMAIL PROTECTED]
web:http://www.a2q.com

The A2Q Method (tm) -- What do you want to improve today?




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Essex Summer School in Social research Methods: 2001

[Eric Tanenbaum]

Please draw this to the attention of your colleagues. 


 The 34'th Essex Summer School 
  in 
 Social Science Data Analysis 
 and
 Collection 

  7 July - 17 August 2001 


This year's Essex Summer School in Social Science Data Analysis
and Collection will offer over 50 one and two-week
introductory, intermediate and advanced courses on
topics which include:

social survey design and analysis, sampling, 
regression, multilevel analysis, time series analysis, 
correspondence analysis, log linear analysis, latent class analysis, 
discourse analysis, game theory, rational choice, social theory, 
data visualisation and data mining, social network analysis, 
maximum likelihood estimation and limited dependent variables, 
structural equation models, qualitative data analysis,
focus groups, interviewing, participant observation, content analysis,
SPSS, Amos, Lisrel,
British Household Panel Survey, time budget collection and Analysis and
comparative policy analysis. 

New courses this year are:

Logit, Probit and Other Generalised Models
Introduction to Geographical Information Systems
Socio-Legal Research Methods
Advanced Social Network Analysis
Dimensional Analysis
Evaluation Analysis

There will be a two-week "data confrontation" workshop on 
"National and International Crime Victimization Surveys". 

A small number of ESRC bursaries are available to participants from 
British academic institutions. 
  
For further details see URL  
or 
e-mail [EMAIL PROTECTED] 
or 
write to
The Essex Summer School in Social Science Data Analysis and Collection
University of Essex 
Colchester, Essex CO4 3SQ, 
United Kingdom 
or 
Fax [international] 44-1206-873598 [UK/Eire] 01206-873598 
or 
telephone [international] 44-1206-872502 [UK/Eire] 01206-872502. 



Eric Tanenbaum
Dept of Government
University of Essex
Colchester, Essex CO4 3SQ
England
(Phone: [UK] 01206-872506 or 01206-872502
[Int'l] 44-1206-872506 or 44-1206-872502)




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Re: basic stats question

[Richard A. Beldin]

This is a multi-part message in MIME format.
--20D27C74B83065021A622DE0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

I have long thought that the usual textbook discussion of independence
is misleading. In the first place, the most common situation where we
encounter independent random variables is with a cartesian product of
two indpendent sample spaces. Example: I toss a die and a coin. I have
reasonable assumptions about the distributions of events in either case
and I wish to discuss joint events. I have tried in vain to find natural
examples of independent random variables in a smple space not
constructed as a cartesian product.

I think that introducing the word "independent" as a descriptor of
sample spaces and then carrying it on to the events in the product space
is much less likely to generate the confusion due to the common informal
description "Independent events don't have anything to do with each
other" and "Mutually exclusive events can't happen together."

Comments?

--20D27C74B83065021A622DE0
Content-Type: text/x-vcard; charset=us-ascii;
 name="rabeldin.vcf"
Content-Transfer-Encoding: 7bit
Content-Description: Card for Richard A. Beldin
Content-Disposition: attachment;
 filename="rabeldin.vcf"

begin:vcard 
n:Beldin;Richard
tel;home:787-255-2142
x-mozilla-html:TRUE
url:netdial.caribe.net/~rabeldin/Home.html
org:BELDIN Consulting Services
version:2.1
email;internet:[EMAIL PROTECTED]
title:Professional Statistician (retired)
adr;quoted-printable:;;PO Box 716=0D=0A;Boquerón;PR;00622;
fn:Richard A. Beldin
end:vcard

--20D27C74B83065021A622DE0--



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Re: Hungry? arnyj

[Tony T. Warnock]

Magyar?



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Re: Do I need to do a Bonferroni/Dunn test?

[Thom Baguley]

Jason Cohen wrote:
> 
> Hi,
> 
> I'm trying to finish my dissertation and a person on my committee raised
> the question of me having to do a Bonferroni correction.  Here is the
> situation.  I have 5 subjects that I have tested at 5 different times
> for 2 different conditions (cued and uncued).  When I do a repeated
> measures ANOVA, I get the the difference between the two conditions over
> those 5 seperate times is statistically significant.  Now, I also have a
> baseline condition that I want to compare the cued and uncued conditions
> to at each of the 5 times individually.  For example, I want to compare
> Baseline value to cued at time 1, then Baseline to cued at time 2, etc.
> To do these comparisons, I use a paired t-test and a significance level
> of 0.05.  The person on my committee suggests that the p-value should be
> adjusted to be 0.01 to correct for atleast 5 comparisons of cued, and
> the same when uncued is compared to baseline.
> 
> I hope what I said makes sense.  I'm not a statistician but I  could use
> help, because from my reading on Bonferroni, I don't think I have to
> make those corrections.  If you have suggestions, please e-mail me at
> [EMAIL PROTECTED]

It depends on what you want to find out. If you expect the cued condition to
outperform the uncued then the main effect of condition seems sufficient to
provide evidence for this. What can the t tests add to this (given the small
n) unless you expect the different time points to show different effects? The
bonferonni correction (and paired t tests) seems relevant only if there is
some theoretical reason to follow the infividual time points. On the other
hand a specific contrast might well be a more sensible and more powerful way
to test any predictions.

Thom


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Re: On inappropriate hypothesis testing. Was: MIT Sexism & statistical bunk

[Irving Scheffe]

Rich,

Both Radford Neal and I have asked
for a statistical rationale supporting
your claim that a significance test
that you advocated
can provide useful information when applied
to the MIT senior biologist data. You
haven't provided one. Instead, you
cite from a web statistics guide which
in turn provides no rationale.

It is now quite apparent that you
have no rationale, only prejudices.
This may be acceptable to the people
who come to you for consulting, but
this is a different forum, with different
standards.

Further comments are interspersed:



On Thu, 22 Feb 2001 18:21:41 -0500, Rich Ulrich <[EMAIL PROTECTED]>
wrote:

>On Mon, 19 Feb 2001 04:27:24 GMT, [EMAIL PROTECTED] (Irving
>Scheffe) wrote:
>
>> In responding to Rich, I'll intersperse selected comments with
>> selected portions of his text and append his entire post below.
>
> - I'm not done with the topic yet.  But it is difficult to go on from
>this point.
>
>I think the difficulty is that JS has constructed his straw-man
>argument about how "hypotheses" are handled; and since it 
>is a stupid strategy, it is easy for him to claim that it is fatally
>flawed.

All the referents are unclear. I didn't construct any straw man
arguments, and you haven't made clear what you are talking about.
You are the one who examined nonrandom data, representing citation
counts over a 12 year period for senior male and female MIT biologists
matched for year of Ph.D.  You look at these data, which
show a HUGE difference in performance between the men and women,
and declare that a significance test is necessary. But you
cannot provide any mathematical justification for the test.

I gave several examples to try to jar you into realizing that
a statistical test on the data cannot answer the question you
want answered.

>
>From his insistence on his "examples,"  it seems to me that he
>believes that someone else is committed to using p-levels in a strict
>way, by beating 5%.  

Not so. If you were following the logic of the many examples I've
presented, you could see that you can construct a reductio ad
absurdem for any of the types of significance tests you are
proposing. If I believed strictly in hypothesis testing 
with a 5% significance level, I doubt that I'd have written
an extensive article advocating confidence interval replacements
for many of the classic hypothesis tests employed in the social
sciences, and giving the precise, exact procedures for
constructing these confidence intervals.


>That's certainly not the case for me, and I
>doubt if anyone defends or promotes it, outside of carefully designed 
>Controlled Random Experiments.
>

It is not the case for me, either, and so everything that follows is
irrelevant.

>Despite the fact that I could not make sense of WHY he wanted
>his example, it turns out -- after he explains it more -- that my own
>analysis covered the relevant bases.  I agree, if you don't have
>"statistical power,"  then you don't ask for a 5%  test, or (maybe) 
>any test at all.  The JUSTIFICATION for having a test on the MIT
>data is that the power is sufficient to say something.  

In order to talk meaningfully about "power", you have to have
a statistical rationale. As I have repeated numerous times,
you have no statistical rationale. You simply "feel like"
you "should" compute a statistical test, when all the assumptions
on which the procedure is based are violated in the data you
are applying the procedure to.

Power to detect what? Under what distributional assumptions?


>
>And what it said is that Jim did BAD INFERENCE.  I said that a 
>couple of times.  I regret that I may have confused people with
>unnecessary words about "inference."
> Outlier =>  No central tendency =>  Mean is BAD  statistic;
>careful reader insists on more or better information before asserting
>there's a difference.

What "outlier" are you referring to? What statistical rule did you 
use to determine the "outlier"?

The MIT paper included all the raw data. At no point did I or my 
coauthor state that we were doing inference on means. (Actually,
a 2 sample t-test done on these data is significant at the .05 
level, but we never imagined computing one.)

Here are the raw data for the citation counts for the 5 senior
MIT female biologists and 6 males who graduated from 1970-76.

MalesFemales
---
128302719
113131690
106281301
 43961051
 2133 935
  893
---

These data are based on 12 years worth of records, from 1989-2000.
The above could be broken down in numerous other ways. For example, we
could produce citation counts per year, try to perform some kind of
correction for the highly specific areas the individuals publish in,
etc. Time series could be examined. 

However, these data are anything but a random sample. MIT is one of
the most selective universities in the world in terms of whom it
hires. 


>
>I asserted that more than once.
>
>Optimistically, my