ETS explicitly says on page 14 of https://www.ets.org/pdfs/gre/gre-math-conventions.pdf that it’s population. If they refer to the sample standard deviation, this will be clear.
ETS explicitly says on page 14 of https://www.ets.org/pdfs/gre/gre-math-conventions.pdf that it’s population. If they refer to the sample standard deviation, this will be clear.