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 sample mean charges for each of the eight categories are shown in the table

$\begin{array}{ccc}\hline \text {Primary Specialty }& \text {Foreign Grad }& \text {USA Grad} \\\hline \text {GP} & 40.10 & 42.50 \\ \text {IM }& 51.80 & 49.50 \\ \text {PED }& 23.60 & 25.40 \\ \text {FP }& 35.60 & 39.40 \\\hline\end{array}$

What type of design was used for this experiment?

A) completely randomized design with two treatments
B) eight treatments
C) 2 x 2 factorial design with 160 replications
D) 4 x 2 factorial design with 20 replications