Someone stopped by today with a power calculation and I asked what software they used. They showed me something I had not seen before, a program developed by the Department of Biostatistics at Vanderbilt University (more specifically, William Dupont and Walton Plummer). The Vanderbilt Biostatistics Department is run by Frank Harrell, so you can be pretty sure that anything that they develop will be high quality. Continue reading
Author Archives: pmean
PMean: A non-technical answer to why we need Markov Chain Monte Carlo
Someone was looking for examples of illustrative examples to help explain to people without a statistical background how MCMC methods can be applied to help solve real world problems. I offered up some general advice and some of my own research as an example. Continue reading
Recommended: Research vs Quality Improvement
I ran across a one page handout in PDF format that discussed the difference between research and quality improvement. It was written from the perspective of the IRB (Institutional Review Board) at UMKC. It’s a nice summary, although the topic is a bit more complex than a single page handout might imply. This is a good starting point for deciding what type of study you want to do. Continue reading
PMean: Finding interesting peer-reviewed articles that illustrate statistical tests
Someone asked how do you find peer-reviewed articles that use simple statistical tests so your students can see the structure of papers that report on statistical analyses. I do this a lot for this blog and for lectures that I give, so I wrote up some suggestions. Continue reading
PMean: What problems does introversion cause for a statistical consultant?
Someone posed an interesting question on the Statistics Consulting message board of the American Statistical Association. To paraphrase, her question was what sort of difficulties would an introvert have in statistical consulting and how do you teach those introverted consultants to overcome those problems. Here’s what I wrote. Continue reading
Recommended: R #6 in IEEE 2015 Top Programming Languages, Rising 3 Places
This Revolutions blog talks about a fairly rigorous evaluation of popular programming languages done by the Institute of Electrical and Electronics Engineers (known by most people by its acronym, IEEE). The list shows all programming languages, including general purpose programming languages. Java C, and C++ are at the top of the list, but R, a language pretty much dedicated to data analysis, is number 6 on the list (up three places from the previous year. Quite an impressive showing. I have mentioned another webpage, http://r4stats.com/articles/popularity/, that compares R and other statistical software packages, and that is worth reading as well. Continue reading
PMean: My H-index
It’s a silly number, perhaps, but I tried to calculate my H-index today. The H-index lists your publications in order from the most cited to the least cited and then finds the value where rank order equals the number of citations. My h-index is 24 which means that I have 24 papers that have been cited 24 or more times. Confused? Here’s a better explanation from Wikipedia. Anyway, I used Research Gate to get an approximation to this (I’m not sure if Research Gate has an accurate citation count). Continue reading
PMean: The pros and cons of cluster randomized trials
I’m helping out a researcher with sample size justification for a cluster randomized trial. I may write a bit about that soon, but in the process of double checking my formulas and calculations, I ran across several articles that discussed the pros and cons of cluster randomized trials. Continue reading
PMean: I want to learn (learn more) about R
I get a lot of questions along the lines of “I want to learn R, can you help me?” or “Where can I learn more about R?” or some other variation. These questions are usually from people who are total beginners or who have just started with R. I don’t have a good answer for them, because learning anything new is hard. But let me try here to outline a few things you can do. Some of these, I have no personal experience with, but have heard recommendations. Continue reading
PMean: How do you select variables for a risk adjusted model?
I was helping a colleague write a response to a reviewer who asked about a risk adjusted model. How did you select the variables for adjustment? He/she speculated that we had used some type of stepwise selection. I used to do this, but stopped doing it in favor of adjusting for any or all variables that were known or suspected to be important. There are serious problems with screening using stepwise approaches to select variables for risk adjustment. But the literature is quite complex and there is no apparent consensus on what is best. Here are some quotes from a few publications about this issue. Continue reading