What is the test for a finding of misconduct for abuse of discretion?

An appellate court reviews a trial court's decision regarding whether or not to conduct an investigation of juror misconduct for abuse of discretion. (People v. Cleveland (2001) 25 Cal.4th 466, 478.) "In determining whether misconduct occurred, '[w]e accept the trial court's credibility determinations and findings on questions of historical fact if supported by substantial evidence. [Citations.] Whether prejudice arose from juror misconduct, however, is a mixed question of law and fact subject to an appellate court's independent determination. [Citations.]' [Citation.]" (People v. Majors (1998) 18 Cal.4th 385, 417.)