It's meaning #4 here:
RoverConcise Oxford English Dictionary © 2008 Oxford University Press:
- 1 in a natural or raw state; not yet processed or refined: crude oil.
- 2 made or done in a rudimentary or makeshift way: a relatively crude nuclear weapon.■ (of an estimate) approximate.
- 3 offensively coarse or rude, especially in relation to sexual matters.
- 4 Statistics (of figures) not adjusted or corrected.
- For Teachers