I was having trouble with trailing blanks in an R program. There were some strings that looked like ” Y” and “Y ” and it’s easy enough to fix this, but one of the “Y ” values was not converting properly. The second character wasn’t a blank, but it looked like it. Here’s what I had to do. Continue reading

# Category Archives: Statistics

# PMean: A p-value of .000

Dear Professor Mean, I ran a statistical test in SPSS and got a p-value of .000. I re-ran the same data in Microsoft Excel and got a p-value of 3.9433E-9. I know from scientific notation that this is the same as 0.0000000039433. Why are these numbers different? Continue reading

# PMean: Extremely imbalanced multi-center trials

There was some recent discussion of issues with multi-center trials where one center dominates, contributing as much as 94% of all the patients. What does this do to the generalizability of the study. I wanted to summarize these comments here, because it relates to some of the issues I’m looking at right now in accrual models for multi-center trials. Continue reading

# PMean: Getting out of the free consulting trap

Someone on the Statistical Consulting Section message board asked a question about how to handle a situation where a colleague was repeatedly asking for advice. How do you make a transition from offering free advice to getting paid as a consultant? There were lots of good answers, and here’s the suggestion that I offered. Continue reading

# PMean: How big is the stuff I’m working on

I have been working part-time on a project for the Great Plains Collaborative (GPC) under the direction of Russ Waitman and the gentle guidance of Dan Connolly, both at Kansas University Medical Center. I hoping to submit a paper soon on the work I’ve done, but if you are curious about the size and scope of the electronic health records that I’ve been slinging around, this blog entry might help. Continue reading

# PMean: Obnoxious use of red text in RStudio

I really enjoy using RStudio, but one thing about it drives me bats. It seems to use red text for some very innocuous error messages. Continue reading

# PMean: My areas of expertise

I was asked to list my areas of expertise for an upcoming Q&A webinar that I am helping with. Here’s the list I shared. Continue reading

# PMean: Will the baby walk away?

I submitted a cute probability problem to the Riddler section of Nate Silver’s Five Thirty Eight web site. Here’s a cut-and-paste of the problem. Continue reading

# Recommended: Medicare Claims Synthetic Public Use Files (SynPUFs)

The Centers for Medicare & Medicaid Services (CMS) provides researchers with access to Medicare claims data, which is a wonderful resources. But you have to sign a restrictive agreement before they will give you this data and you have to pay a non-trivial amount of money to get the data. Fair enough, because CMS has to guarantee patient confidentiality among other things. But what if you want to “play” with the data before taking the plunge? Thankfully, CMS has provided to the general public a synthetic (read fake) data set that has the same data structure. This allows you to prototype your programs on the synthetic data and then transition easily to the real data. Continue reading

# PMean: Are systematic overviews reliable?

*Dear Professor Mean, I’m helping a student with a piece of work and he described systematic reviews as being reliable. I’m troubled by this on a number of fronts.* Continue reading