Distance Learning

Thanks to all who have recommended directories of distance learning courses for statistics. I have posted links at http://core.ecu.edu/psyc/wuenschk/DistanceEd.htm . ~~~ Karl L. Wuensch, Departm

RE: Statistical illiteracy

Don asked: "But back to your retail trade: if they advertise a 150% discount directly, without referring to the sequence of three 50% discounts, might they not be liable to legal action for misrepresentation?" Perhaps in the distant past, when our government attempted to protect the rights of

RE: Statistical illiteracy

I came across a table of costume jewelry at a department store with a sign that said "150% off. "  I asked them how much they would pay me to take it all off of their hands.  I had to explain to them what 150% meant, and they then explained to me how percentages are computed in the retail t

ANOVA = Regression

For a demonstration of the equivalence of regression and traditional ANOVA, just point your browser to http://core.ecu.edu/psyc/wuenschk/StatHelp/ANOVA=reg.rtf. -Original Message- From: Stephen Levine [mailto:[EMAIL PROTECTED]] Sent: Tuesday, December 11, 2001 3:47 AM To: Karl L.

Experimental Correlation Coefficients

My experimental units are 100 classrooms on campus. As I walk into each room I flip a perfectly fair coin in a perfectly fair way to determine whether I turn the room lights on (X = 1) or off (X = 0). I then determine whether or not I can read the fine print on my bottle of smart pills (

RE: When does correlation imply causation?

Dennis warns "the problem with this is ... does higher correlation mean MORE cause? lower r mean LESS cause? in what sense can think of cause being more or less? you HAVE to think that way IF you want to use the r value AS an INDEX MEASURE of cause ..." Dennis is not going to like this, since he

RE: Maximized lambda4

Dennis asked "how do we know what a test's true reliability is?" Osburn knew because he simulated true-score covariance matrices and from these obtained observed score covariance matrices as a function of the true-score matrices and hypothetical values of reliability. More details are in

Maximized lambda4

Callender and Osburn (Educational and Psychological Measurement, 1977, 37, 819-825) developed a method for estimating maximized lambda4, the greatest split-half reliability coefficient among all possible split halves for a scale. The method is quite tedious to do by hand, and the authors

RE: p value

Dennis wrote: " it is NOT correct to say that the p > value (as traditionally calculated) represents the probability of finding a > result LIKE WE FOUND ... if the null were true? that p would be ½ of > what is calculated." Jones and Tukey (A sensible formulation of the signific

Confidence Intervals for Estimates of Effect Sizes

A week or so ago I suggested the following: "Some of those who think that estimation of the size of effects is more important than the testing of a nil hypothesis of no effect argue that we would be better served by reporting a confidence interval for the size of the effect. Such confidence int

RE: Are parametric assumptions importat ?

Lise advised "I tell my students that the ANOVA is not robust to violation of the equal variances assumption, but that it's a stupid statistic anyway.  All it can say is either, "These means are equal," or "There's a difference somewhere among these means, but I can't tell you where it is.

Standardized Confidence Intervals

Some of those who think that estimation of the size of effects is more important than the testing of a nil hypothesis of no effect argue that we would be better served by reporting a confidence interval for the size of the effect. Such confidence intervals are, in my experience, most often report

Bimodal distributions

Does a bimodal distribution necessarily have two modes? This might seem like a silly question, but in my experience many folks apply the term "bimodal" whenever the PDF has two peaks that are not very close to one another, even if the one peak is much lower than the other. For example, D

RE: analytical aptitude

Alan opined "2. I would find 'ability to think analytically' hard to distinguish from 'mathematical aptitude' - although I accept that some narrow definitions of both characteristics may have minimal overlap." Well, I am no cognitive psychologist or psychometrician, but my inclination wo

RE: Flatland

x27;s description of his world. ======== "Wuensch, Karl L." wrote (inter alia): > > If you have read Edwin Abbott's "Flatland," you might recognize that the > same concept (a mean) which looked like a point in one dimensiona

memorizing formulas

I sure many of you have been asked a question like that posed today by one of my students, and I would be interested in hearing how you respond to it. I've included the question along with the response I gave this morning. It looks a bit long to me now, I must have been having an attack

RE: t-test normality assumption

Some Monte Carlos I've done suggest that when the population is distinctly skewed, the distribution of t is distinctly different from that of Student's t, even when the sample size is large enough for the distribution of sample means to be approximately normal.

Statistical Methods in Psychology Journals

The APA's Task Force on Statistical Inference has published an article in the American Psychologist in which they present the changes they are planning on recommending be made in the APA Publication Manual. The citation is: Wilkinson, L. & Task Force on Statistical Inference. (1999). Statistic