Hi
On 8 Feb 2002, Thomas Souers wrote:
2) Secondly, are contrasts used primarily as planned
comparisons? If so, why?
There are a great many possible contrasts even with a relatively
small number of means. If you examine the data and then decide
what contrasts to do, then you have in some
Hi
On 30 Jan 2002, Wuzzy wrote:
Anyway I'm currently going on the definition of adjusted for 1 2 and
3 as the following equation:
adjusted variable=variable^-variable
(where variable-hat represents the variable predicted by 1 2 and 3 in
a multivariate equation and variable is just the
Hi
On Thu, 24 Jan 2002, Rich Ulrich wrote:
On 24 Jan 2002 07:09:23 -0800, [EMAIL PROTECTED] (Rich Einsporn)
wrote:
Jim Clark gave a fine answer to the question posed by Sangdon Lee.
However, I am curious about the correlation and R-square figures given by
Sangdon. Apparently, the R
Hi
On 23 Jan 2002, Sangdon Lee wrote:
I have one Y and two Xs (X1 and X2), and am trying to perform multiple
linear regression. All Xs and Y variables are standardized (zero mean
and unit variance). X1 and X2 are moderately correlated (r=0.6) and
the correlation of X1 and X2 to Y is -0.2
Hi
On Tue, 18 Dec 2001, Benjamin Kenward wrote:
Let's say you have a repeatable experiment and each time the result can be
classed into a number of discrete categories (in this real case, seven).
If a treatment has no effect, it is known what the expected by chance
distribution of results
Hi
On 6 Dec 2001, David Heiser wrote:
Most of the focus is on structural equation modeling (SEM). For
statisticians, a quick referral to Jim Steiger's article Driving Fast in
Reverse in JASA March 2001, p331-p338 (if you have it around) is a quick
discourse on SEM and the inherent problems
Hi
On 3 Dec 2001, Karl L. Wuensch wrote:
I think that phrase has created much misunderstanding. I try
to convince my students that correlation is necessary but not
sufficient for establishing a causal relationship.
And I teach that NEITHER presence NOR absence of _simple_
correlation can be
Hi
On Thu, 29 Nov 2001, Stan Brown wrote:
But -- and in retrospect I should have seen it coming -- some
students framed the hypotheses so that the alternative hypothesis
was the drug is effective as claimed. They had
Ho: p = .9; Ha: p .9; p-value = .9908.
You might point out to
Hi
On Tue, 27 Nov 2001, Thom Baguley wrote:
I'd argue that they probably aren't that independent. If I ask three
questions all involving simple algebra and a student doesn't
understand simple algebra they'll probably get all three wrong. In
my experience most statistics exams are better
Hi
On 25 Nov 2001, Herman Rubin wrote:
If it is a good test, ability should predominate, and there is
absolutely no reason for ability to even have close to a normal
distribution. If one has two groups with different normal
distributions, combining them will never get normality.
I think
Hi
On 28 Nov 2001, Dennis Roberts wrote:
At 01:35 PM 11/28/01 -0600, jim clark wrote:
The distribution of grades will depend on the distribution of
difficulties of the items, one of the elements examined by
psychometrists in the development of professional-quality
assessments.
unless
Hi
On 16 Nov 2001, Rich Strauss wrote:
I've just done some quick simulations in Matlab, constructing randomized
null distributions of the t-statistic under both scenarious: (1) sample
variances based on sample means vs. (2) variances about the pooled mean.
Assuming I've done everything
Hi
On 15 Nov 2001, dennis roberts wrote:
in the moore and mccabe book (IPS), in the section on testing for
differences in population proportions, when it comes to doing a 'z' test
for significance, they argue for (and say this is commonly done) that the
standard error for the difference
Hi
On Thu, 15 Nov 2001, Jerry Dallal wrote:
But, if the null hypothesis is that the means are the same, why
isn't(aren't) the sample variance(s) calculated about a pooled
estimate of the common mean?
What you are testing is whether there is more variability between
groups than you would
Hi
On 2 Nov 2001, Donald Burrill wrote:
On Fri, 2 Nov 2001, jim clark wrote:
I would hate to ressurect a debate from sometime in the past
year, but the chi-squared is a non-directional (commonly referred
to as two-tailed) test, although it is true that you only
consider one end (tail
Hi
On Thu, 18 Oct 2001, Wouter Duyck wrote:
Suppose i have a factorial design with two between-subject factors (one
factor A of 3 levels and one factor B of 2 levels) en two within-subject
factors (one factor C of 2 levels and one factor D of 5 levels). Of course,
to perform an ANOVA on this
Hi
On 4 Oct 2001, Edwina Chappell wrote:
Permutations versus Combinations. Easy ways to understand
the concepts and distinguish when to use?
I use to like to teach both as a specific variant of the
partition rule, and then the distinction was whether specific
problems involved so many sets
Hi
On 26 Sep 2001, Burke Johnson wrote:
R Pretest Treatment Posttest
R PretestControl Posttest
In the social sciences (e.g., see Pedhazur's popular
regression text), the most popular analysis seems to be to
run a GLM (this version is often called an ANCOVA), where Y
is the
Hi
On Thu, 20 Sep 2001, @Home wrote:
Is there any downloadable freeware that can generate let's say 2000 random
samples of size n=100 from a population of 100 numbers.
Is this conceivable? for excel etc.
Easily done with various statistical software (e.g., SPSS, SAS),
if you have access
Hi
On 13 Sep 2001, Rolf Dalin wrote:
Hi, this is about Jim Clark's reply to dennis roberts.
I'm not sure how both informative gets translated into neither
very informative. Seems like a perverse way of thinking to me.
Moreover, your original question was then what benefit is there
to
Hi
On 13 Sep 2001, Herman Rubin wrote:
jim clark [EMAIL PROTECTED] wrote:
Or consider a study with a small effect size that is significant.
The fact that the effect is significant indicates that some
non-chance effect is present and it might very well be important
theoretically or even
Hi
I found the Rosenthal reference that addresses the following
point:
On 13 Sep 2001, Herman Rubin wrote:
The effect size is NOT small, or it would not save more
than a very small number of lives. If it were small,
considering the dangers of aspirin, it would not be used
for this purpose.
Hi
On 12 Sep 2001, dennis roberts wrote:
At 07:23 PM 9/12/01 -0500, jim clark wrote:
What your table shows is that _both_ dimensions are informative.
That is, you cannot derive effect size from significance, nor
significance from effect size. To illustrate why you need both,
consider
Hi
On 12 Sep 2001, Dennis Roberts wrote:
given a simple effect size calculation ... some mean difference compared to
some pooled group or group standard deviation ... is it not possible to
obtain the following combinations (assuming some significance test is done)
Hi
On 29 May 2001, Alex Yu wrote:
Does anyone know any book/paper/website about teaching the relationship
between ANOVA and regression? I have Data Analysis for Research Designs
by Keppel. I also seached www.jstor.org but could not find anything.
I am interested in seeing what approaches
Hi
On 24 May 2001, David Heiser wrote:
Be careful on your assumptions in your models and studies!
---
Placebo Effect An Illusion, Study Says
By Gina Kolata
New York Times
(Published in the Sacramento Bee, Thursday, May 24, 2001)
...
He and
Hi
On 15 May 2001, Alan McLean wrote:
The usual test for a simple linear regression model is to test whether
the slope coefficient is zero or not. However, if the slope is very
close to zero, the intercept will be very close to the dependent
variable mean, which suggests that a test could be
Hi
On 3 May 2001, Warren Sarle wrote:
Joel Best is a professor of sociology and criminal
justice at the University of Delaware. This essay is
excerpted from _Damned Lies and Statistics:
Untangling Numbers From the Media, Politicians, and
Activists_, just published by the University of
Hi
On 25 Apr 2001, Alan McLean wrote:
I agree - although students do need tables in (written) exams... But
we use a computer program called Tuteman in our teaching and testing, so
the natural way to find critical values or p-values is via the computer
- we use Excel mainly. In general, I
Hi
On 24 Apr 2001, Mark W. Humphries wrote:
I concur. As I mentioned at the start of this thread, I am self-learning
statistics from books. I have difficulty telling what is being taught as
necessary theoretical 'scaffolding' or 'superceded procedures', and what one
would actually apply in a
Hi
On Fri, 20 Apr 2001, dennis roberts wrote:
At 10:58 AM 4/20/01 -0500, jim clark wrote:
What does a t-distribution mean to a student who does not
know what a binomial distribution is and how to calculate the
probabilities, and who does not know what a normal distribution
is and how
Hi
On 7 Apr 2001, Dianne Worth wrote:
After several years of frustration with SAS, I am migrating
to SPSS. I am currently working on a project in both
packages, to ensure accuracy of results as I teach myself
SPSS. I would like to obtain 1) the squared semi-partial
correlation based on
Hi
I like to use small, artificially generated data sets with
integer parameters to introduce analyses. Often, however, I find
it difficult to avoid undesirable contingencies among the scores
(e.g., linear dependencies in within-subject designs). Is there
an algorithmic way to generate such
Hi
On 12 Mar 2001, Radford Neal wrote:
Yes indeed. And the context in this case is the question of whether
or not the difference in performance provides an alternative
explanation for why the men were paid more (one supposes, no actual
salary data has been released).
In this context, all
Hi
On Mon, 12 Mar 2001, Irving Scheffe wrote:
Jim:
For example, suppose you had a department
in which the citation data were
Males Females
12220 1298
2297 1102
When I said outlier, I had in mind hypothetical data of the
following sort (it doesn't matter to me whether
Hi
On Tue, 6 Feb 2001, Thom Baguley wrote:
Donald Burrill wrote:
Well, it _might_ be. Depends on what hypothesis was being tested,
doesn't it? And so far "rjkim" hasn't deigned to tell us that.
Yes, though I think the vocabulary can obscure what goes on. To me a
"one-tailed" test
Hi
On Sat, 20 Jan 2001, Bob Wheeler wrote:
I can't find a paper by anyone named Cohen with a
title resembling what you give in CIS. Perhaps you
can improve the citation.
Cohen, J. (1968). Multiple regression as a general data-analytic
system. Psychological Bulletin, 70, 426-443.
Best
Hi
On Wed, 27 Dec 2000, T.S. Lim wrote:
In article [EMAIL PROTECTED],
jim clark [EMAIL PROTECTED] wrote:
On Tue, 26 Dec 2000, John Uebersax wrote:
IMHO, psychological tests in this case should not substitute for a
thorough interview and human judgment.
scores
Hi
On 27 Dec 2000, Jeff Rasmussen wrote:
scores, but not in aggregating them). In general, human judgment
does not fare all that well relative to actuarial (i.e.,
statistical) methods. Interesting that someone posting to a
statistical newsgroup would advocate the non-statistical approach
Hi
On Tue, 26 Dec 2000, John Uebersax wrote:
IMHO, psychological tests in this case should not substitute for a
thorough interview and human judgment.
Just my .02 worth.
There is a considerable literature on clinical judgment (i.e.,
interview and human judgement) vs. actuarial predictions
Hi
On 29 Feb 2000, Magill, Brett wrote:
I am planning to design a study of an educational program. Of interest is
the decay over time of knowledge and skills learned through the program.
Specifically, we want to know if there is a point in time when the rate of
decay changes (a steady drop
Hi
On Wed, 22 Dec 1999, Peter Westfall wrote:
Jim Clark wrote:
Artificially giving all students (or almost all) the same grade
does not minimize variation in the underlying trait, achievement,
in this case. It simply hides the variation so that one does not
know to what extent one
HI
On 7 Dec 1999, Magill, Brett wrote:
I am a graduate student in sociology studying individual's perceptions of
control (locus of control) using existing data. The data set include four
items to measure this construct which were taken from a larger scale of more
than twenty, the larger
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