The administrative president of a health maintenance organization (HMO) is attempting to show the benets of managed health care to an insurance company. The president believes certain types of doctors are more cost-effective than others. One theory is that the area of specialty that a doctor serves is an important factor in measuring the cost-effectiveness. Doctors serve in one of four primary areas of specialty: General Practice (GP), Internal Medicine (IM), Pediatrics (PED), and Family Physicians (FP). The average total charges per member per month for each of the specialties were recorded. A second factor which the president believes inuences the average total charges per member per month is whether the doctor is a foreign or USA medical school graduate. To investigate this, the president also collected data on 20 foreign medical school graduates in each of the four primary specialty areas and 20 USA medical school graduates in each of the four primary specialty areas. The results of the ANOVA are summarized below. ANOVA SourceofVariatbn 55 at MS F P~value F on (.05! Specidty 2255 7618 61.1048 564845-26 2.664107 Med sd'lool 105 1 5 0.842216 0360217549 3333366 Interaction 890 3 297 2.382269 0071684478 2.664107 Vlflthin 18950 152 124.6711 Total 42330 159 What degrees of freedom should be used to determine the critical value of the F ratio against which to test for differences in the average total charges per member per month for doctors among the four primary specialty areas? 0 ndf = 3, ddf = 152 o ndf = 1, ddf = 159 o ndf = 1, ddf = 152 o ndf = 3, ddf = 159