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.
$$\begin{array} { l c } \text { Group } & \text { Sample Mean } \\\hline \text { IM } & 55.9 \\\text { GP } & 41.4 \\\text { FP } & 40.00 \\\text { PED } & 21.50\end{array}$$ Which primary specialties have significantly lower mean charges than Internal Medicine (IM) ?

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