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 primary specialty is an important factor in measuring the cost-effectiveness of physicians. To investigate this, the HMO obtained independent random samples of 20 HMO physicians 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. In order to compare the mean charges for the four specialty groups, the data were be subjected to a one-way analysis of variance. The results of the Tukey analysis are summarized below. $$\begin{array} { c c } \text { Group } & \text { Sample Mean } \\\hline \text { IM } & 55.9 \\\text { GP } & 41.4 \\\text { FP } & 39.00 \\\text { PED } & 24.60\end{array}$$ Which primary specialties have significantly lower mean charges than Internal Medicine (IM) ?

A) PED
B) PED and FP
C) PED, FP, and GP
D) none