What is the test for establishing probable cause when an informant reports illegal activity?

"An informant's description of illegal activity is sufficient to establish probable cause if the totality of the circumstances indicate that the tip is reliable." United States v. Elliott, 893 F.2d 220, 223 (9th Cir.), amended on other grounds, 904 F.2d 25, cert. denied, 498 U.S. 904 (1990). For an informant's information to support a finding of probable cause, the affidavit should support an inference that the informant is trustworthy and that the informant's observations of criminal activity were made in a reliable way. United States v. Landis, 726 F.2d 540, 543 (9th Cir.), cert. denied, 467 U.S. 1230 (1984). When an informant's information is corroborated by other averments in the affidavit, the informant is likely to be reliable. See United States v. Miller, 753 F.2d 1475, 1480 (9th Cir.1985).