Many times, researchers will categorize continuous variables. For example, birth weight of human infants is often categorized as “low birth weight” vs. “normal”; sometimes it is “very low birth weight”, “low birth weight” and normal. The cutoff for low birth weight is usually 2.5 kg. IQ tests are categorized with labels such as “gifted”. Depression tests are categorized. And so on. This rarely makes sense, either statistically or substantively. Read more!
I got into a conversation on Twitter (find me there as @peterflomstat) about the user-friendliness of statistical software. I have heard R described (appropriately, I think) as being “expert friendly”. This led to a conversation about whether and when that is good or bad. But we agreed that it would be hard to discuss that in 140 character blocks. Read more!