"Can Mom's Drinking Lower Kids' IQ?" examined the relationship between mothers' consumption of alcohol during pregnancy and their children's IQs. The mothers were classified as being abstainers (0 alcoholic drinks per day), light drinkers (up to 0.5 per day), moderate drinkers (0.5 to 1 per day), or heavy drinkers (more than 1 per day). Is alcohol consumption being treated as a categorical or a quantitative variable?