Class certification is governed by Code of Civil Procedure section 382, which provides in part: "When the question is one of a common or general interest, of many persons, or when the parties are numerous, and it is impracticable to bring them all before the court, one or more may sue . . . for the benefit of all." Code of Civil Procedure section 382 authorizes a class action when a plaintiff meets his or her burden to establish the existence of a well-defined community of interest among an ascertainable class. (Sav-On Drug Stores, Inc. v. Superior Court (2004) 34 Cal.4th 319, 326; Lockheed Martin Corp. v. Superior Court (2003) 29 Cal.4th 1096, 1103-1104.) "The certification question is 'essentially a procedural one that does not ask whether an action is legally or factually meritorious.' A trial court ruling on a certification motion determines 'whether . . . the issues which may be jointly tried, when compared with those requiring separate adjudication, are so numerous or substantial that the maintenance of a class action would be advantageous to the judicial process and to the litigants.' " (Sav-On Drug Stores, Inc. v. Superior Court, supra, 34 Cal.4th at p. 326; Bartold v. Glendale Federal Bank (2000) 81 Cal.App.4th 816, 829 "At a class certification hearing, the court should not make any determination of the merits or validity of the claim.") "We review the trial court's ruling for abuse of discretion. 'Because trial courts are ideally situated to evaluate the efficiencies and practicalities of permitting group action, they are afforded great discretion in granting or denying certification. . . . Accordingly, a trial court ruling supported by substantial evidence generally will not be disturbed "unless (1) improper criteria were used ; or (2) erroneous legal assumptions were made " . . . . "Any valid pertinent reason stated will be sufficient to uphold the order." ' " (Sav-On Drug Stores, Inc. v. Superior Court, supra, 34 Cal.4th at pp. 326-327; Kaldenbach v. Mutual of Omaha Life Ins. Co. (2009) 178 Cal.App.4th 830, 844 "We may not reverse, however, simply because some of the court's reasoning was faulty, so long as any of the stated reasons are sufficient to justify the order.") When a certification order turns on disputed facts or inferences to be drawn from the facts, " ' " 'the reviewing court has no authority to substitute its decision for that of the trial court.' " ' " (Sav-On Drug Stores, Inc. v. Superior Court, supra, 34 Cal.4th at p. 328.) In California, Code of Civil Procedure section 382 authorizes class action suits when "the question is one of a common or general interest, of many persons, or when the parties are numerous, and it is impracticable to bring them all before the court ... ." (Code Civ. Proc., 382.) "Drawing on the language of Code of Civil Procedure section 382 and federal precedent, our Supreme Court has articulated clear requirements for the certification of a class. The party advocating class treatment must demonstrate the existence of an ascertainable and sufficiently numerous class, a well-defined community of interest, and substantial benefits from certification that render proceeding as a class superior to the alternatives." (Brinker Restaurant Corp. v. Superior Court (2012) 53 Cal.4th 1004.) The proponent of certification carries the burden of demonstrating a well-defined community of interest among class members; as a threshold, the proponent must show there are predominant common questions of law and fact applicable to the whole class. (Norwest Mortgage, Inc. v. Superior Court (1999) 72 Cal.App.4th 214, 221.) We review the allegations of the complaint, the declarations of the attorneys and the evidence introduced at the certification hearing below to decide if the trial court correctly determined the plaintiff satisfied its burden of showing that common issues predominate over individual issues among the class members. (Ibid.) Common issues predominate when they would be "the principal issues in any individual action, both in terms of time to be expended in their proof and of their importance. . . ." (Vasquez v. Superior Court, supra, 4 Cal.3d at p. 810.) "The ultimate question in every case of this type is whether, given an ascertainable class, the issues which may be jointly tried, when compared with those requiring separate adjudication, are so numerous or substantial that the maintenance of a class action would be advantageous to the judicial process and to the litigants." ( Collins v. Rocha (1972) 7 Cal.3d 232, 238, 102 Cal. Rptr. 1, 497 P.2d 225.) Class actions will not be permitted where there are diverse factual issues to be resolved, despite the existence of common questions of law. ( Brown v. Regents of University of California (1984) 151 Cal. App. 3d 982, 988-989.) "If the ability of each member of the class to recover clearly depends on a separate set of facts applicable only to him or her, then all of the policy considerations which justify class actions equally compel the dismissal of such inappropriate actions at the pleading stage." ( Id. at p. 989.)"Because a class should not be certified unless 'substantial benefits accrue both to litigants and the courts' ," a party seeking certification must demonstrate "a class action would be superior to individual lawsuits ." (Basurco v. 21st Century Ins. Co. (2003) 108 Cal.App.4th 110, 120; Brinker Restaurant Corp. v. Superior Court (2012) 53 Cal.4th 1004 at p. 1021 "The party advocating class treatment must demonstrate . . . substantial benefits from certification that render proceeding as a class superior to the alternatives".) Along the same lines, "'because group action also has the potential to create injustice, trial courts are required to "'carefully weigh respective benefits and burdens and to allow maintenance of the class action only where substantial benefits accrue both to litigants and the courts.'" '" (Newell v. State Farm General Ins. Co. (2004) 118 Cal.App.4th 1094, 1101; City of San Jose v. Superior Court (1974) 12 Cal.3d 447, 459.) "In deciding whether a class action would be superior to individual lawsuits, 'the court will usually consider four factors: (1) The interest of each member in controlling his or her own case personally; (2) The difficulties, if any, that are likely to be encountered in managing a class action; (3) The nature and extent of any litigation by individual class members already in progress involving the same controversy; and (4) The desirability of consolidating all claims in a single action before a single court.'" (Basurco, at p. 121.)