Jay Tanzman wrote:
>I agree that you can test a hypothesis by using an observational study, but
>that
>does not make it an experiment. The original poster was looking for a
>definition to use in a lecture, and an experiment, by definition, involes
>assignment of treatments to experimental units.
Art Kendall wrote:
>In SPSS output ignore the lines for equal variances, and use the lines for
>unequal variances.
Last year on this group, there was an interesting dataset posted, in which the
equal and unequal variance t tests give very different results:
Temperatures from Portion 1 of a st
>I have a question about creating biplots from *existing* output by
>PCA, canonical variates analysis (CVA) and correspondence analysis.
>
Legendre & Legendre 1998, Numerical Ecology, 2nd ed, Elsevier, Amsterdam
provides excellent descriptions of the different ways of displaying biplots and
their
Rich Ulrich wrote:
>I am not positive, but
>I think I would have objected to "equal % change"
>as =proportionate= by the time I finished algebra in high school.
>
>I know I have objected to similar confusion, on principled
>grounds, since I learned about Odds Ratios.
>
>I suspect that the
His definition of proportionate would mean that if a group's approval of Bush
went from 1% to 31%, that too would be proportionate. The relative odds would
be one way of expressing the changes in proportions, but the absolute
difference (60% to 90% is roughly propotionate to an increase from 33%
The Gallup organization posted a video to explain why the the increase in
black's job approval for Bush is 'proportionate' to the increase among whites.
Both increased by about 30% (60 to 90 for whites, mid thirties to roughly 70%
for blacks), so the increase is proportionate, not disproportionat
In the current issue of JSE, William Peterson's column "Topics for discussion
from current newspapers and journals" includes links to articles about 2001
being "The year of the shark":
http://www.amstat.org/publications/jse/v9n3/peterson.html
Peterson includes a summary of Paulos's NY Times comm
>Andrew Morse wrote:
>
>>Who was the first to say "Correlation does not imply causation" in so many
>>words? I know that the idea dates back to David Hume, but Hume did his
>>work about a century before the term "correlation" acquired its modern
>>statitical meaning.
>
>It certainly wasn't Hume,
Andrew Morse wrote:
>Who was the first to say "Correlation does not imply causation" in so many
>words? I know that the idea dates back to David Hume, but Hume did his
>work about a century before the term "correlation" acquired its modern
>statitical meaning.
It certainly wasn't Hume, who's ar
Hollander, M. and D. A. Wolfe. 1999. Nonparametric Statistical Methods, 2nd
edition. John Wiley & Sons, New York. 787 p. {Encyclopedic, but not as easy
to read as many of the others cited. The notes on each test provide good
discussions and references to recent advances}
===
Dr. Mecklin,
Thanks so much for your post about the TI83 calculator. On a hunch, I looked at the MCAS instructions page. The boxplot problem was asked in Section 3 of the 3-d test, and in the final 2 sections, students were encouraged to bring their graphing calculators. The MCAS test writers s
During the last week in August, there was a lengthy thread on sci.stat.edu
about problems with the probability and statistics questions in MCAS, the high
stakes test required for graduating from a MA public high school.
Shortly after participating in that thread, I wrote up my analyses of 6 of th
Robert Chung wrote
>Yike, Rich. Are you still sore that Bonds left the Pirates? Go
>back and check the entire thread. This thing started because on
>July 13, Eugene Gall quoted an article in "Slate" that invoked
>regression to the mean to "prove" that Bonds wouldn't hit 70.
I did post the origina
Donald Burrill wrote:
>If the data are normally distributed (or even approximately so, what
>seems to be called "empirically distributed" these days), the 3rd
>quartile + 1.5 IQR locates a point 2.0 std. devs. above the mean;
>symmetrically, the 1st quartile minus 1.5 IQR gets you 2.0 SDs belo
I got an email from Anand Vaishnav, the Globe reporter who did Friday's article
on the math and stats problems in MCAS. Only about 50% of the 63000 10th
graders in MA got median and range. I suspect that mean and range probably was
the most popular incorrect answer (according to the MCAS graders
NCTS should be NCTM in my previous post
The NCTM web page, with links to their boxplot (different from the Tukey
boxplot) is at:
http://www.nctm.org/
For some reason, the NCTM boxplot extends the whisker to cover all data outside
the box, thus completely gutting the major role of the Tukey boxplo
Hans Waldmann wrote:
Actually we need to evaluate whether factorial structures
>of 2 tests are similar enough, roughly, to assume they're parallel. For my
>own part I think one should use LISREL (or the like), constrain the loadings
>of one model to the other one, and evaluate (mis)fit. It shouldn
I just took another look at the front page Boston Globe article that described
the most difficult MCAS question. The most difficult question on the 2001 math
test is a question involving probability and geometry, question 9 on the MCAS
test
http://www.doe.mass.edu/mcas/01release/
I've seen versio
Robert Dawson wrote:
> An obvious approach that would seem to give the advantages hoped for
>from the focussed test without the disadvantages would be just to group
>questions in the original test in roughly increasing order of
>difficulty. One might (I'm not so sure that this would be a go
Dennis Roberts wrote:
>
>At 12:31 PM 8/27/01 +, EugeneGall wrote:
>> The Harcourt-Brace description of the boxplot, which is now being taught
>>to MA students, isn't a proper boxplot (maybe the Harcourt-Brace K-12
>boxplot
>>is different from the Tukey boxpl
Dennis Robers wrote:
>eugene ... first of all ... how come your email ID always gets bounced
>back???
I added a nospam to the address to limit spam.
>now, certainly, you are not saying are you that if they "fail" this test
>the first time they take it in the 10th grade ... when it is given ... th
Jay Warner wrote:
>Trusting that Eugene or someone in Massachusetts can respond, I ask,
>
>Are box and whisker plots included in the material that _must_ be taught
>in the
>K-12 curriculum? I believe a previous post pointed out that older intro stat
>books, including those listed as suitable for
David Winsemius wrote
>Here are the three stated competencies that the test is supposed to measure:
>http://www.doe.mass.edu/mcas/01release/
>1) Select, create, and interpret an appropriate graphical representation
>(e.g.,
>scatterplot, table, stem-and-leaf plots, box-and-whisker plots, circle
>gr
comment at end
dennis roberts wrote:
>i would say however ... that IF the test included only 6 items related to
>statistics ... out of the larger test ... then the issue of whether in a
>boxplot ... the vertical bar ... or .. in old minitab a + ...
>
>Boxplot
>
>
> -
>From: [EMAIL PROTECTED] (dennis roberts)
>the only purpose it can serve ... and i am not saying this is important .
>is to know that the median is part of a boxplot ... just like you might
>want them to identify what the | are at the ends ... the hinges ... just as
>you might want them to kno
Some of the MCAS stats and probability questions were tough but fair. I
disagreed vehemently with one question:
Question 39 on the 10th grade Math 2001 test.
It showed a Tukey boxplot and asked whether the graph represented a mean and
range or a median and range.
Now, this question will do one
Paige Miller wrote:
>EugeneGall wrote:
>>
>This hardly "PROVES" anything. It is more a statement about what has
>happened in the past.
"Proves" was in the original article. I'm assuming Ellenberg, a mathematics
prof, was using 'proves' in a
I'd like to note that Ellenberg is really "off base" into thinking that Galton
was fooled by RTM into thinking that breeding would reduce diversity. As
Stigler's "Statistics on the Table" documents, Galton was initially fooled by
RTM, but then worked out the mechanism behind RTM and showed that r
> (J. Williams) wrote:
>Since the envelopes containing the absentee ballots were separated
>from the ballots themselves, no information about the voter was
>available: "The Times asked Gary King, a Harvard expert on voting
>patterns and statistical models, what would have happened had the
>flaw
NMDS can get trapped in local minima. It is advisable to use several random
configurations as starting points and choose the solution with the lowest
Stress (Kruskal or Young's - I don't have a preference). I checked SPSS and it
doesn't have a random initial configuration that I could see. That
Jordan Ellenberg, in today's Slate, PROVES that Bonds won't break the
HR record because of regression to the mean. The argument is a
little sloppy, but there is definitely some RTM involved:
"If our discussion above is correct, then hitters who
lead the major leagues in home runs at the All-
>From: [EMAIL PROTECTED] (Donald Burrill)
>There must be constraints on the values of the three variables.
>Commonly used for situations like a chemical mixture of 3 components.
>Each component can have a relative concentration between 0% and 100%,
>but if component A is at 100%, components B
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