Expert witnesses may base opinions on facts or data that the expert “has been made aware of or personally observed.” Fed.R.Evid. 703. If the facts and data relied upon are the sort that experts in that field would reasonably rely on, then those facts “need not be admissible for the opinion to be admitted." Id. Accordingly, experts may base their opinions on otherwise-inadmissible information, such as hearsay, so long as the information is the sort reasonably relied upon in the experts' field.