What is the test for a judge to recall a sentence that has been found to be disparate?

In the present case, it is clear that the trial court has met the obligations imposed upon it by statute and by People v. Herrera, supra, 127 Cal.App.3d 590, 179 Cal.Rptr. 698. Herrera established a two-part analysis: (1) the trial court must determine whether a sentence is in fact disparate; and (2) if the sentence is found to be disparate, the judge must then decide whether to recall the sentence using the "observed sentencing pattern" as a guideline. (At pp. 601-602, 179 Cal.Rptr. 698.)