, in excersing such power, must "evaluate the evidence presented and determine whether or not the jury has come to a rationally based conclusion." Spence v. Bd. of Educ. of the Christina Sch. Dist., 806 F.2d 1198, 1201 (3d Cir. 1986); see also Evans, 273 F.3d at 354 ("[T]he issue to be decided here `is no