Hi, Margaret. I've given some thought to your problem; here's a
restatement of it, and a few thoughts.
Recapitulating, in case I've misunderstood a small point or three,
you have "a 3-factor experiment", by which I assume you mean a
complete, balanced, crossed design: R(AxBxC) for observat
On Sun, 24 Jun 2001, Melady Preece wrote in part:
> I am teaching educational statistics for the first time, and although I
> can go on at length about complex statistical techniques, I find myself
> at a loss with this multiple choice question in my test bank. I
> understand why the range of
On 17 Jun 2001, Marc wrote (edited):
> I have to summarize the results of some clinical trials.
> The information given in the trials contain:
>
> Mean effects (days of hospitalization) in treatment & control groups;
> numbers of patients in the groups; p-values of a t-test (of the
> differen
On 11 Jun 2001, srinivas wrote:
> I have a problem in identifying the right multivariate tools to
> handle datset of dimension 1,00,000*500. The problem is still
> complicated with lot of missing data.
So far, you have not described the problem you want to address, nor the
models you think
On Fri, 8 Jun 2001, Julie Dechy wrote:
> Textbooks say to not adjust group means for a covariate when their
> regression lines are not parallel, since mean differences depend upon
> the value of the covariate.
>
> But, what exactly are adjusted group means in the presence of
> interaction? A
On Fri, 8 Jun 2001, Mike Tonkovich wrote:
> I ran an analysis of covariance using PROC GLM (in SAS) with an
> interaction statement. My understanding was that a nonsignificant
> interaction term meant that the slopes were the same,
Not exactly. It means only that differences in the slopes,
On 3 Jun 2001, Bekir wrote, in part:
> My aim was to compare groups 2, 3, 4, 5 with control (group 1)". ...
>
> The rewiever had written me: "Accordingly, a "statistical penalty"
> needs to be paid in order to account for the increased risk of a Type
> 1 error due to multiple comparisons. T
On 2 Jun 2001, Bekir wrote in part:
> I performed a study on " different enteral nutrients and bacterial
> translocation in experimental obstructive jaundice."
>
> There was 5 groups of rats. Each group consists of 20 rats. Occurred
> Translocation incidences in mesenteric lymph nodes were show
On 1 Jun 2001, Francis Dermot Sweeney wrote:
> Say I have three set of data x,y,z.
I'll assume that you mean "I have three variables, x, y, z."
(One cannot in general perform a regression analysis unless the variables
of interest are in the same data set, not in three separate data sets.)
On Thu, 31 May 2001, W. D. Allen Sr. wrote:
> Only from the education field do we hear the statement that over ninety
> percent of students ranked above the median! The statement was made on
> TV.
(1) I take it that it was the keyword "students" that led you to suppose
that the statement h
On Tue, 29 May 2001, Peter Nash wrote:
> Do you know any statistical software shows on a scatter-plot when
> points are coincident (i.e. there are numerous points that overlap in
> one location)? This is sometimes shown using jitter, sometimes
> different sizes for the points, sometimes addin
On Tue, 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.
Alex, if you haven't encountere
On Fri, 18 May 2001, auda wrote (slightly edited):
> In my experiment, [when] two dependent variables DV1 and DV2 [were]
> analyzed separately with ANOVA, the independent variable [IV (with ]
> two levels IV_1 and IV_2) modulated DV1 and DV2 differentially:
>
> mean DV1 in IV_1 > mean DV1 in IV
yOn Sat, 12 May 2001, RD wrote, inter alia:
> The only approach to deal with z test for means that I have seen so
> far was using s^2 = s1^2/n1 + s2^2/n2 formula.
> t test is always using pooled variance.
I think not _always_. _Usually_, because (i) there is seldom
a strong need to
If the mean of the predictor X is zero, the intercept is equal to the
mean of the dependent variable Y, however steep or shallow the slope
may be. And as Jim pointed out, the standard error of a predicted value
depends on its distance from the mean of X (being larger the farther
away it is fr
On Sat, 12 May 2001, Alexandre Kaoukhov (RD <[EMAIL PROTECTED]>) wrote:
> I am puzzled with the following question:
> In z test for continuous variables we just use the sum of estimated
> variances to calculate the variance of a difference of two means i.e.
>s^2 = s1^2/n1 + s2^2/n2.
N
On Thu, 10 May 2001, Magill, Brett wrote, inter alia:
> How should these data be analyzed? The difficulty is that the data
> are cross level. Not the traditional multi-level model however.
Hi, Brett. I don't understand this statement. Looks to me like an
obvious place to apply multilevel
If I have grossly misunderstood the problem, the comments below may not
be helpful; except perhaps in helping you clarify what may have turned
out to be unintended ambiguities in the original post.
On Sun, 6 May 2001, Dr C van Oldenbeek (alias Albert Einstein) wrote
(comments & questions emb
Short answers below; which may or may not adequately address the lurking
questions you had in mind.
On Fri, 4 May 2001, Jeff wrote:
> Would like to ask [for] help with the following questions:
>
> 1. why designs for experiments should be orthogonal ?
So that results for each factor, and each
I rather think the problem is not adequately defined; but that may
merely reflect the fact that it's a homework problem, and homework
problems often require highly simplifying assumptions in order to be
addressed at all. See comments below.
On Fri, 4 May 2001, Adil Abubakar wrote:
> My name
Thanks, Rich. My semi-automatic crap detector hits DELETE when it sees
things like this anyway; but... did you notice that although SamFaz
(or whoever, really) claims to cite a bill passed by the U.S. Congress
he she or it is actually writing from Canada?
I'm not quite sure what to m
On Tue, 1 May 2001, Dale Glaser wrote in part:
> a colleague just approached me with the following problem at
> work: he wants to know the number of possible combinations of boxes,
> with repeats being viable...so, e.g,. if there are 3 boxes then
> what he wants to get at is the follow
On Wed, 18 Apr 2001, Giuseppe Andrea Paleologo wrote:
> I am dealing with a simple conjecture. Given two generic positive
> random variables, is it always true that the sum of the quantiles (for
> a given value p) is greater or equal than the quantile of the sum?
>
< snip, technical t
Interesting response, Bill. But I don't believe it.
Can you enumerate the combinations you perceive?
-- DFB.
On Sat, 28 Apr 2001, W. D. Allen Sr. wrote:
> Five different condiments, plus no condiments, means 6*5*4*3*2*1 = 720
> distinct combinati
On Sat, 28 Apr 2001, Abdul Rahman wrote:
> Please help me with my statistics.
>
> If you order a burger from McDonald's you have a choice of the
> following condiments: ketchup, mustard , lettuce. pickles, and
> mayonnaise. A customer can ask for all these condiments or any subset
> of them
On Fri, 27 Apr 2001, Lise DeShea wrote in part:
> I teach statistics and experimental design at the University of
> Kentucky, and I give journal articles to my students occasionally with
> instructions to identify what kind of research was conducted, what the
> independent and dependent varia
On Mon, 23 Apr 2001, jim clark wrote:
> On 22 Apr 2001, Donald Burrill wrote:
> > If I were doing it, I'd begin with a "full model" (or "augmented model",
> > in Judd & McClelland's terms) containing three predictors:
> > y = b
The clearest (and withal concise) exposition of ANCOVA that I ever
encountered is at the beginning of the third chapter of Tatsuoka's book
on multivariate analysis. If you can find a copy, it would both explain
what ANCOVA is all about, and illuminate the more cryptic responses
you've already
On Tue, 10 Apr 2001, Gary Carson wrote:
> It's the proportion of success (x/n) which has approxiatmenly a normal
> distribution for large n, not the number of success (x).
Both are approximately normal.
(If the r.v. W = (x/n) is (approximately) normally distributed, then
the r.v. V = x = n*W
On Mon, 9 Apr 2001, Rich Ulrich wrote:
> On Mon, 09 Apr 2001 10:44:40 -0400, Paige Miller
> <[EMAIL PROTECTED]> wrote:
>
> > "Andrew L." wrote:
>
AL> I am trying to learn what a t-test will actually tell me, in
> simple terms. < snip >, but i still dont quite
> understand the significance.
>
On Wed, 4 Apr 2001, Erik <[EMAIL PROTECTED]> wrote:
> What is the p-value of a t-statistic significant (significant level
> shown by the software is p) in the wrong direction in an one-tailed
> test? Should we modified it to (1-p)? Or it is just p?
Well, first you need to be sure it's reportin
Everything you need is in what you wrote.
You do understand that "z" is the usual shorthand for "a standard score",
and that a standard score is the representation of a given raw score as
its deviation from the population mean in standard-deviation units?
The rest is merely a lookup in a tabl
On Fri, 30 Mar 2001 [EMAIL PROTECTED] wrote:
> Donald Burrill writes:
>
> > On Thu, 29 Mar 2001, H.Goudriaan wrote in part:
> >
> > > - my questionnaire items are measured on 5- and 7-point Likert scales,
> >
> > > and consequently not (bivariate
On Thu, 29 Mar 2001, H.Goudriaan wrote in part:
> - my questionnaire items are measured on 5- and 7-point Likert scales,
> so they're not measured on an interval level
Non sequitur.
> and consequently not (bivariate) normally distributed;
Real data hardly ever is. Do you need it to
On Wed, 14 Mar 2001, Scott wrote:
> I am uncertain about the solution to the problem for which I am trying
> to solve. I am hoping that someone might help guide me to the correct
> solution.
First you'll have to be rather clearer about what the
problem is. Comments embedded be
On Thu, 15 Mar 2001, dennis roberts wrote in part:
> ps ... a conclusion that lots of people don't agree with one another
> will not be too helpful
Maybe not, but it sure would be realistic -- which might be reassuring
to some of our students who have their own doubts on that score about our
On Tue, 13 Mar 2001, Will Hopkins wrote in part:
> Example: you observe an effect of +5.3 units, one-tailed p = 0.04.
> Therefore there is a probability of 0.04 that the true value is less
> than zero.
Sorry, that's incorrect. The probability is 0.04 that you would find an
effect as large a
On Fri, 9 Mar 2001, Wei Xiao wrote:
> Suppose I went to 10 lakes. I want to measure the relation with water
> temperature (WT) and air temperature (AT). So I can do a regression
> with these 10 points like this:
> |*
> |*
Hi, Rich. The only answer I recall having seen on the listserve was one
suggesting multilevel (aka "hierarchical") modelling. If one wanted to
address the problem without ML modelling, I'd be inclined to proceed as
follows:
(1) I assume, in the absence of commentary to the contrary, that t
In response to dennis roberts, who wrote in part:
>
> > i see "inventing" some algorithm asnot quite in the same
> > genre of developing a process for extracting some enzyme from a
> > substance ... using a particular piece of equipment specially
> > developed for that purpose
> > i hope w
Dennis also included [EMAIL PROTECTED] among his addressees,
but I am not on that list and therefore cannot reply to them...
On Tue, 6 Mar 2001, dennis roberts wrote:
> may eons ago ... 1974 to be precise ... i had this idea of making a
> small plastic normal and skewed curve template ... tha
On Mon, 5 Mar 2001, Philip Cozzolino wrote in part:
> Yeah, I don't know why I didn't think to compute my eta-squared on the
> significant trends. As I said, trend analysis is new to me (psych grad
> student) and I just got startled by the results.
>
> The "significant" 4th and 5th order trends
In response to Dennis's earlier statement,
"that is ... power in many cases is a highly overrated CORRECT decision"
I wrote:
> >Well, no. Overrated it may be (that lies, I think, in the eye of the
> >beholder); but a _decision_ it is definitely not. Power is the
> >_probability_ of making a
On Sun, 4 Mar 2001, dennis roberts wrote in part:
> i know that sometimes power is "defined" as 1 - beta ... but, beta
> could therefore (algebraically and logically) be defined as 1 - power
Only for the conditional definition of power; I would wish to add the
conditional clause "when the nu
On Sat, 3 Mar 2001, dennis roberts wrote:
> when we discuss things like power, beta, type I error, etc. ... we
> often show a 2 by 2 table ... similar to
>
> null truenull false
>
> retain correct type II, beta
>
> reject type I, alpha po
On Sun, 4 Mar 2001, Philip Cozzolino wrote in part:
> However, after the cubic non-significant finding, the 4th and 5th
> order trends are significant.
>
> Intuitively, it seems that if there is no cubic trend of significance,
> there will not be any higher order trend, but this is relatively
On Sat, 3 Mar 2001, Arenson, Ethan wrote:
> Would someone please remind me the formula for Fisher's
> z-transformation of correlation coefficients?
Z = 0.5 log[(1 + r)/(1 - r)] (using the natural logarithm).
Its standard error is 1/sqrt(n - 3) ("sqrt" = "square root of").
To con
Hi, Esa!
You've had a couple of responses; here's another.
You state "pairwise comparisons"; but it strikes me as at least
possible that you might want (or might _also_ want) to consider more
complex comparisons if any such comparisons seemed to offer a more
parsimonious (or
On Sat, 24 Feb 2001, Mike Granaas wrote:
> Interesting point. Yes, if the Ss do something other than a random guess
> the binomial model would be violated. The question then becomes what
> would they do if they are uncertain? I suspect that they would fall back
> on visual inspection...which p
You'll need to tell us more before anyone can be much help.
1. Is there only one treatment A, or are there several treatments to
be compared?
2. Is "time" important (in the sense of length of time between initial
and final measures, for example, not just in distinguishing
I note that in the literature cited, the word "nauseam" (in the Latin
phrase "ad nauseam") is misspelled both times it appears.
-- DFB.
On Sat, 17 Feb 2001, Jeff Rasmussen wrote:
> a spoof on the glut of journals:
>
> http://psych
If (as I suppose) you're asking about the special wired program in the
TI-60X for carrying out correlation computations conveniently, I cannot
help you; just checking to make sure you aren't asking for the usual
procedure for any dumb-calculator-with-limited-storage, implementing
the customar
On Thu, 8 Feb 2001, jim clark wrote in part:
> We all agree that it is confusing, but I do believe that the use
> of one-tailed and two-tailed to refer to directional vs.
> non-directional hypotheses (rather than uniquely to one or two
> tails of a distribution) is very wide-spread and quite comm
Two comments: (1) You have not told us what other distribution(s) are
possible; in the absence of this information it is imopssible to assess
how likely it may be for one particular datum to have "come from" (i.e.,
to have been randonly drawn from) the distribution of interest.
(2) You cann
If for each Subject you have 4 Measures in each of the 3 Conditions, then
both Conditions and Measures are repeated-measures factors: you design
may be symbolized as S x C x M -- that is, Subjects (5 levels) are
crossed with both Conditions and Measures. This design is equivalent to
R(S
On Thu, 8 Feb 2001, dennis roberts wrote in part:
> MTB > ttest 5 c1
>
> One-Sample T: C1
>
> Test of mu = 5 vs mu not = 5
>
> Variable N Mean StDev SE Mean
> C1 20-0.082 0.914 0.204
>
> Variable 95.0% CIT P
> C1
On Tue, 6 Feb 2001, jim clark wrote in part:
> The problem is that one-tailed test is taken as synonymous with
> directional hypothesis (e.g., Ha: Mu1>Mu2). This causes no
> confusion with distributions such as the t-test, because
> directional implies one-tailed. This correspondence does not
>
I 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.
And on Tue, 6 Feb 2001, Thom Baguley replied:
> Yes, though I think the vocabulary can obscure what goes on. To me a
> "one-tailed" test should re
On Mon, 5 Feb 2001, dennis roberts wrote:
> would this be like the F being less than 1 ... in a regular anova???
> mean difference not even varying like we would expect them to by chance
> if null were true?
Well, it _might_ be. Depends on what hypothesis was being tested,
doesn't it? And s
On Mon, 5 Feb 2001, "June" wrote:
> Isn't a chi-square test inherently a 'one-sided sig. test'?
Not inherently. The common (most common?) application, in testing the
hypothesis of independence of classification systems in a two-way table
of frequencies, is a one-sided test, of course. But t
On Sun, 4 Feb 2001, Jay Warner wrote (inter alia), replying to Paul
Jeffries:
> Say I look at a pressure gauge. A clear 0 (absolute zero pressure -
> space), and measurable, even incremented units. Increase in pressure
> from 100 psi to 101 psi is the same increase as from 0.1 psi to 1.1 ps
You've had a good "flash response" from Jay Warner.
Other short answers embedded in original query below:
On Sat, 3 Feb 2001 [EMAIL PROTECTED] wrote:
> I have two factors A and B and I want to run a DOE to study my
> response. My factor B is at 3 levels; (900, 1450 and 2000) , my factor
> A
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