The perils of categorizing continuous variables
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. Continue reading 'The perils of categorizing continuous variables'»