A Certain HMO Is Attempting to Show the Benefits of Managed

A certain HMO is attempting to show the benefits of managed health care to an insurance company. The HMO believes that certain types of doctors are more cost-effective than others. One
Theory is that both primary specialty and whether the physician is a foreign or USA medical school
Graduate are an important factors in measuring the cost-effectiveness of physicians. To investigate
This, the president obtained independent random samples of 40 HMO physicians, half foreign
Graduates and half USA graduates, from each of four primary specialties-General Practice (GP) ,
Internal Medicine (IM) , Pediatrics (PED) , and Family Physician (FP) -and recorded the total
Per-member, per-month charges for each. Thus, information on charges were obtained for a total
Of n = 160 doctors. The ANOVA results are summarized in the following table. $\begin{array}{lrrrrr}\text { Source } & \text { df } & \text { SS } & \text { MS } & \text { F Value } & \text { Prob > F } \\\hline \text { Specialty } & 3 & 22855 & 7618 & 60.94 & .0001 \\\text { Medschool } & 1 & 105 & 105 & 0.84 & .6744 \\\text { Interaction } & 3 & 890 & 297 & 2.38 & .1348 \\\text { Error } & 152 & 18950 & 125 & & \\\hline \text { Total } & 159 & 42800 & & & \\\hline\end{array}$

Assuming no interaction, is there evidence of a difference between the mean charges of USA and foreign medical school graduates? Use $\alpha = 0.05$ .

A) No, because the test for the interaction is not significant at $\alpha = 0.05$ , the test for the main effect for medical school is not valid.
B) No, the test for the main effect for medical school is not significant at $\alpha = 0.05$ .
C) Yes, the test for the main effect for medical school is significant at $\alpha = 0.05$ .
D) It is impossible to make conclusions about the main effect of medical school based on the given information