In summer 2015 I picked all the topics for my A-to-Z; I didn’t work up the courage to ask for topics until the next time around. Some, I remember why I chose. I’m not sure why I picked Quintile, as a statistics term, rather than quartile. Both are legitimate terms, and circle around a similar idea. That is that we need to know how data is distributed: what range of numbers are common, what ones are rare. I wonder if I wasn’t saving ‘quartile’ for some later A-to-Z, for fear of running out of Q terms. Or if I felt that quartiles were familiar enough that quintiles would seem a touch strange. That is the sort of thing I’d likely do.