In the early part of any epidemiology course, few things throw students as much as computing age-adjusted mortality. It seems really counter-intuitive that two populations could have the exact same mortality rate and yet one is significantly less healthy than the other. Thinking about it for a moment, though, before diving into computation, makes it…
Policy makers have very good reason for wanting to know how common a condition or disease is. It allows them to plan and budget for treatment facilities, supplies of medication, rehabilitation personnel. There are two broad answers to the question, “How common is condition X?” and, interestingly, both of these use the exact same SAS…
Who was it that said asking a statistician about sample size is like asking a jeweler about price. If you have to ask, you can’t afford it. We all know that the validity of a chi-square test is questionable if the expected sample size of the cells is less than five. Well, what do you…
On twitter, there were a few comments from people who said they didn’t like to take interns because “More than doing work, they want to watch me work.” I see both sides of that. You’re busy. You’re not netflix. I get it. On the other hand, that’s a good way to learn. The data are…
How common is a particular disease or condition? It depends on what you mean by common. Do you mean how many people have a condition, or do you mean how many new cases of it are there each year? In other words, are you asking about the probability of you HAVING a disease or of you GETTING…
Even though Rick Wicklin (buzzkill!) disabused me of the concern that SAS was communicating with aliens through the obscure coding in its sashelp data sets, I still wanted to roll my own. If you, too, feel more comfortable with a data set you have produced yourself, let me give you a few tips. There is…
I was going to write about prevalence and incidence, and how so-called simple statistics can be much more important than people think and are vastly under-rated. It was going to be cool. Trust me. In the process, I ran across two things even more important or cooler (I know, hard to believe, right?) Here’s what…
I’ll be teaching a graduate course in epidemiology in the spring and giving a talk on biostatistics at SAS Global Forum in April, so I thought I’d jump ahead and start rambling on about it now. When I tell people that I teach epidemiology, the first question I usually get is, What’s epidemiology? In short,…
When I first taught multivariate statistics, I was nervous. The material is more difficult than Statistics 101 so I assumed teaching the course would be more difficult as well. Over 25 years of teaching, I’ve found the opposite. The more advanced you get in a field, the easier the courses are to teach. You might…
The results are in! The chart below gladdens my little heart, somewhat. One thing to note is the fact that the 95% confidence interval is comfortably above zero. Another point is that it looks like a pretty normal distribution. What is it? It is the difference between pretest and post-test scores for 71 students at…