I used to know this 25-cent word, and I have forgotten it. It describes a phenomenon where common descriptive statistics like mean and variance misrepresent the individuals or maybe the phenomenon itself. (I don't know because I can't look it up!) I believe it begins with an e, probably an en- or eu-. Does it sound familiar to anyone?
"Children's classroom learning should not be reduced to test scores, because learning is -------- "