What is the test for establishing that there is a single conspiracy?

In this case, to establish the existence of a single conspiracy, the government had to prove that an overall agreement existed among the conspirators. United States v. Bibbero, 749 F.2d 581, 587 (9th Cir.1984), cert. denied, 471 U.S. 1103 (1985). A formal agreement is not necessary; rather, the agreement may be inferred from the defendants' actions pursuant to the scheme or other circumstantial evidence. United States v. Clevenger, 733 F.2d 1356, 1358 (9th Cir.1984). A single conspiracy may involve separate subagreements or subgroups of conspirators. United States v. Tille, 729 F.2d 615, 621 (9th Cir.), cert. denied, 469 U.S. 845 (1984).