What is the test for excluding relevant evidence in a civil case?

Evidence 403 provides that the district court "may exclude relevant evidence if its probative value is substantially outweighed by a danger of . . . unfair prejudice, confusing the issues, [or] misleading the jury," among other concerns not relevant here. Provided the district court "has conscientiously balanced the proffered evidence's probative value with the risk for prejudice, its conclusion will be disturbed only if it is arbitrary or irrational." United States v. Al-Moayad, 545 F.3d 139, 159-60 (2d Cir. 2008) (quotation marks omitted). "To avoid acting arbitrarily, the district court must make a conscientious assessment of whether unfair prejudice substantially outweighs probative value." Id. at 160 (quotation marks omitted).