P.Mean Website (created 1997-12-22, reborn at this location
2008-06-21)
Welcome to the P.Mean website. Here are the
most important links:
Most recent news and announcements (View all
news and announcements for 2008)
- 2008-11-25. The
StATS website is back up and running again. The look is somewhat
different, so as to match the style of the rest of the Children's Mercy
website. The content is pretty much unchanged. They did remove all references
to my new website, as is their prerogative. I will gradually correct my links
in the new site so that I can link back to all my old content. This will take
a while. If you find any errors on my old website (I'm sure you're shocked
that Professor Mean would make any errors), please contact me and I'll make
the appropriate corrections on the new site.
- 2008-11-24. I am getting started again on producing illustrated
case studies of research ethics. I have a main page
for this project and a very early
draft of the TGN 1412 trial in PDF format.
- 2008-11-05. The first issue of the
Monthly Mean newsletter was released today. I hope you like it. If you
haven't signed up yet, it is easy. I am using a
professional service, iContact, so you can be sure that your privacy will be
respected and that you will be able to unsubscribe without a lot of hassles.
- 2008-11-03. Children's Mercy Hospital has shut down the StATS
website, at least temporarily. If you try to go to any page on my old website,
you will get the following message "We're sorry, but the Stats site is
currently being revamped! Please check back soon." I will start
negotiating with Children's Mercy to post the old material at my new website,
but I am unsure how these negotiations will go. The copyright statement that
was originally posted on the website before I tried to change these webpages
to open source stated that individual educational use of these webpages is
acceptable. If anyone has an individual educational need for any particular
webpage at my old site, send me an email and I
will get you a copy. If there is a favorite topic that you want covered at my
new site, let me know and I will develop some new content on that topic that
does not infringe on the copyright of the original page. Many of the links on
this website to the content of the old website are now broken, and I will try
to fix these as soon as possible.
- 2008-11-01. My last day at Children's Mercy Hospital was Friday,
October 31. It has been a wonderful twelve years. I am looking forward to my
new career as an independent statistical consultant,
but I will miss many friendships that I have developed with the people I have
worked with.
The most recent website entries (View all website entries for 2008)
- P.Mean: A false sense of frugality
(created 2008-12-17). A while back I received a data set that was very
well documented, but there was one thing that I wish that the data entry
person had not done. The demographic data was listed as 45f, 52m, 22m, 21f,
etc. This was obvious shorthand for a 45 year old female, 52 year old male,
and so forth.
- P.Mean: Viewing SPSS and SAS output
without buying SPSS and SAS (created 2008-12-17). For one of my consulting
clients, I asked for a copy of the output that the previous statistician had
used. I received two files, one with an SPV extension and another with an MHT
extension. It was obvious from the context that the first was an SPSS output
file and the second was a SAS output file. I have access to both SPSS and SAS
packages, but not conveniently at my laptop. I wanted to look at the files
quickly, so what could I do?
- P.Mean: Using a sub-optimal
approach in meta-analysis (created 2008-12-06). I am having difficulty
understanding the meta-analysis of ordinal data in a Cochrane systematic
review, and would appreciate advice and comments. One study in the
meta-analysis had an ordinal efficacy outcome with categories None, Some,
Good, and Excellent. The meta-analysis did 4 separate analyses, treating each
category as if it were a dichotomous outcome. Aside from the fact that this
generates (almost) more analyses than there are data, this approach seems
unnecessary and uninterpretable. The Cochrane Handbook says: "Ordinal and
measurement scale outcomes are most commonly meta-analysed as
dichotomous data." And "Occasionally it is possible to analyse the data using
proportional odds models where ordinal scales have a small number of
categories, the numbers falling into each category for each intervention group
can be obtained, and the same ordinal scale has been used in all studies."
What should the authors of the systematic review have done?
- P.Mean: What is the Lan-DeMets approach to
interim analysis? (created 2008-11-21). I read an article that talked
about a trial that ended early. They describe the approach as a
"O'Brien-Fleming stopping boundaries determined by means of the Lan-DeMets
approach.". Does anyone you know anything about this statistical technique to
determine if this is a valid approach?
- P.Mean: Ethics of research into
unscientific therapies (created 2008-11-15). What is a responsible
ethical position on research on complementary or alternative medicine that is
not based on "generally accepted" principles of science? For example,
redirecting energy fields in the body; or demonstrating the positive effects
of intercessory prayer (prayer on behalf of another person). It is one thing
for a scientist member to say "I don't think the proposed statistical
methodology is adequate to the task." It's quite another thing to say "I don't
believe that there is any scientific basis for the proposed research." What
then?
Interesting articles, books, quotes, or websites added to this site
recently. (View all interesting articles, books,
quotes, and websites)
- Zotero: The Next Generation Research
Tool. George Mason University. Excerpt: Zotero is an easy-to-use
yet powerful research tool that helps you gather, organize, and analyze
sources (citations, full texts, web pages, images, and other objects), and
lets you share the results of your research in a variety of ways. An extension
to the popular open-source web browser Firefox, Zotero includes the best parts
of older reference manager software (like EndNote)—the ability to store
author, title, and publication fields and to export that information as
formatted references—and the best parts of modern software and web
applications (like iTunes and del.icio.us), such as the ability to interact,
tag, and search in advanced ways. Zotero integrates tightly with online
resources; it can sense when users are viewing a book, article, or other
object on the web, and—on many major research and library sites—find and
automatically save the full reference information for the item in the correct
fields. Since it lives in the web browser, it can effortlessly transmit
information to, and receive information from, other web services and
applications; since it runs on one’s personal computer, it can also
communicate with software running there (such as Microsoft Word). And it can
be used offline as well (e.g., on a plane, in an archive without WiFi).
URL: www.zotero.org
-
Regression with SAS. Chapter 5: Additional coding systems for categorical
variables in regression analysis. Xiao Chen, Phil Ender, Michael
Mitchell, Christine Wells, UCLA Academic Technology Services. Excerpt:
Categorical variables require special attention in regression analysis
because, unlike dichotomous or continuous variables, they cannot by entered
into the regression equation just as they are. For example, if you have a
variable called race that is coded 1 = Hispanic, 2 = Asian 3 = Black 4 =
White, then entering race in your regression will look at the linear effect of
race, which is probably not what you intended. Instead, categorical variables
like this need to be recoded into a series of variables which can then be
entered into the regression model. There are a variety of coding systems that
can be used when coding categorical variables. Ideally, you would choose a
coding system that reflects the comparisons that you want to make. In Chapter
3 of the Regression with SAS Web Book we covered the use of categorical
variables in regression analysis focusing on the use of dummy variables, but
that is not the only coding scheme that you can use. For example, you may want
to compare each level to the next higher level, in which case you would want
to use "forward difference" coding, or you might want to compare each level to
the mean of the subsequent levels of the variable, in which case you would
want to use "Helmert" coding. By deliberately choosing a coding system, you
can obtain comparisons that are most meaningful for testing your hypotheses.
This website was last verified on 2008-URL: www.ats.ucla.edu/stat/sas/webbooks/reg/chapter5/sasreg5.htm
- Helping Doctors and Patients Make Sense of Health Statistics. Gerd
Gigerenzer Wolfgang Gaissmaier Elke Kurz-Milcke Lisa M. Schwartz Steven
Woloshin. Psychological Science in the Public Interest 2008: 8(2); 53-96.
[Abstract]
[PDF]. Excerpt: Many doctors, patients, journalists, and politicians
alike do not understand what health statistics mean or draw wrong conclusions
without noticing. Collective statistical illiteracy refers to the widespread
inability to understand the meaning of numbers. For instance, many citizens
are unaware that higher survival rates with cancer screening do not imply
longer life, or that the statement that mammography screening reduces the risk
of dying from breast cancer by 25% in fact means that 1 less woman out of
1,000 will die of the disease. We provide evidence that statistical illiteracy
(a) is common to patients, journalists, and physicians; (b) is created by
nontransparent framing of information that is sometimes an unintentional
result of lack of understanding but can also be a result of intentional
efforts to manipulate or persuade people; and (c) can have serious
consequences for health.
- Components of placebo effect: randomised controlled trial in patients
with irritable bowel syndrome. T. J. Kaptchuk, J. M. Kelley, L. A. Conboy,
R. B. Davis, C. E. Kerr, E. E. Jacobson, I. Kirsch, R. N. Schyner, B. H. Nam,
L. T. Nguyen, M. Park, A. L. Rivers, C. McManus, E. Kokkotou, D. A. Drossman,
P. Goldman, A. J. Lembo. Bmj 2008: 336(7651); 999-1003.
[Medline]
[Abstract]
[Full text]
[PDF]. Description: The authors suggest that the placebo affect can be
separated into three components: the process of observation itself (the
Hawthorne effect), the therapeutic ritual associated with a placebo, and the
patient-practitioner interactions. They then test this empirically in a three
arm single blind study. There were significant differences between the arms of
the study, and the effect of the patient-practitioner interactions was the
strongest effect.
- The Myth of Equipoise
in Phase 1 Clinical Trials. Adil E. Shamoo, PhD. Posted 11/05/2008 at
Medscape J Med. 2008;10(11):254. Note that a free registriation may be
required. Excerpt: Phase 1 clinical research trials using healthy
volunteers are conducted for the sole purpose of serving the public good (a
utilitarian concept). The literature on equipoise analysis does not exclude
phase 1 trials with controls or healthy volunteers from the claim of being in
"equipoise." The continued perpetuation of this ethically and scientifically
invalid concept undermines the ethics of research with human subjects.
URL: www.medscape.com/viewarticle/582554
- Interesting quote: The statistician who supposes that his main contribution to the planning of an
experiment will involve statistical theory, finds repeatedly that he makes his most
valuable contribution simply by persuading the investigator to explain why he wishes to
do the experiment, by persuading him to justify the experimental treatments, and to
explain why it is that the experiment, when completed, will assist him in his research.
-- Gertrude M. Cox. (I can't recall the original source where I
found this quote. Sorry!)
The most recent personal entries (View all
personal entries for 2008)
-
Steve, Cathy, and Nicholas -- Nicholas the
artist (created 2008-12-05). Until just recently, Nicholas has not taken a great interest in art projects.
There was a recent project, though, that inspired him. The students in his
classroom were all asked to color a turkey as a special character. Nicholas
chose a Spiderman turkey.
- Steve, Cathy, and Nicholas -- The cousins
help decorate cupcakes (created 2008-12-05). We were asked to bring a dessert for the family Thanksgiving dinner, so Cathy
suggested that the younger cousins (Gabriella, Matthew, and Sophia) join us for
a cupcake decorating party. This picture shows Gabriella and Matthew with their
mother, Elizabeth. I think Nicholas and Sophia were already playing at this
time.
- Steve, Cathy, and Nicholas -- Nicholas the
pumpkin carver (created 2008-12-05). Nicholas carved his first pumpkin this year. Cathy showed him where to cut,
but he did all the work himself. Nicholas is showing his scary face in this picture. It's hard to tell who is
more frightening.
- Steve, Cathy, and Nicholas -- My
niece is a blogger (created 2008-11-17). My niece, Kathleen Gier, is
writing a blog about varsity sports for the Kansas City Star. You can view it
at varsity.kansascity.com/user/blogs/3242. She writes about high school sports
with a special emphasis on her high school, Saint Thomas Aquinas, in Overland
Park. She's been doing this for about a month, but today is the first day I
have had time to check it out. She has nine blog entries, so far. I think she
writes quite well, but I may be biased.
- Steve, Cathy, and Nicholas -- Nicholas
loses his first baby tooth (created 2008-09-18). For a couple of weeks,
Nicholas has had a loose tooth. He would show everyone how he could push it
forward until it was almost horizontal. On Sunday, on the way into church
Nicholas shouted out "The wind blew away my tooth." He opened his mouth and
there was a big gap where his loose tooth was.
The most popular pages, excluding home page and various archive pages
(last checked 2008-11-17)
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www.pmean.com/GeneralHelp.html
- www.pmean.com/Evidence.html
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www.pmean.com/testimonials.html
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www.pmean.com/news/2008-11.html
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www.pmean.com/personal/swimmer.html
- www.pmean.com/consult.html
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www.pmean.com/personal/toothless.html
- www.pmean.com/08/Spss17.html
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www.pmean.com/08/SdTooBig.html
- www.pmean.com/resume.html
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www.pmean.com/08/RegressionAndAnova.html
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www.pmean.com/category/SampleSizeJustification.html
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www.pmean.com/08/LikertSum.html
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www.pmean.com/08/CanIAsk.html
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www.pmean.com/category/ModelingIssues.html
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www.pmean.com/category/TeachingResources.html
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www.pmean.com/08/InterveningVariable.html
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www.pmean.com/08/RepeatedMeasuresPart2.html
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www.pmean.com/08/UsingGoogle.html
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www.pmean.com/category/CriticalAppraisal.html
This work is licensed under a
Creative
Commons Attribution 3.0 United States License. This page was written by
Steve Simon and was last modified on
2008-12-17.