What is the test for appeal from an order granting a new trial?

"In sum, the appeal from an order granting a new trial depends upon the sufficiency of the reasons specified by the trial court. Whether these reasons are sufficient depends in turn upon whether there is a substantial basis in the record for the trial judge's decision. [Citations.]" (Bigboy v. County of San Diego, supra, 154 Cal.App.3d at pp. 405-406, 201 Cal.Rptr. 226.)

In Bigboy we held that "it is a futile effort to search the judge's statement of reasons for granting a new trial for any reference to any portion of the evidence that would ... guide an appellate court in determining whether the 'jury clearly should have reached a different verdict.' " (Bigboy v. County of San Diego, supra, 154 Cal.App.3d at p. 406, 201 Cal.Rptr. 226.) The statement of reasons was thus "insufficient as a matter of law." (Id. at p. 408, 201 Cal.Rptr. 226.) In the case before us, by contrast, the evidence relied upon and referred to in the order (expert medical testimony on the issue of causation) is fully adequate both to guide our review and to supply a substantial basis for the order.