What is the test for whether a defendant obstructed justice?

Whether a defendant obstructed justice is a factual determination we review for clear error. See United States v. Barbosa, 906 F.2d 1366, 1369 (9th Cir.1990) If a defendant attempts to obstruct the administration of justice, the offense level shall be increased by two levels. See U.S.S.G. 3C1.1 (1988). Obstruction of justice is defined as testifying untruthfully concerning a material fact at any judicial proceeding. See U.S.S.G. 3C1.1, Application Note 1(c) (1988); United States v. Dunnigan, 507 U.S. 87, 95 (1993); Barbosa, 906 F.2d at 1369.