P.Mean: Main page for the P.Mean website (created 2008-06-21)

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)

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.