(Data file: drug cost) Health plans use many tools to try to control the cost of prescription medicines. For older drugs, generic substitutes that are equivalent to name-brand drugs are sometimes...

(Data file: drug cost) Health plans use many tools to try to control the cost of prescription medicines. For older drugs, generic substitutes that are equivalent to name-brand drugs are sometimes available at a lower cost. Another tool that may lower costs is restricting the drugs that physicians may prescribe. For example, if several similar drugs are available for treating the same symptoms, a health plan may require physicians to prescribe only a few of them. Since the usage of the chosen drug will be higher, the health plan may be able to negotiate a lower price for that drug. The data described in Table 9.6, provided by Mark Siracuse, can be used to explore the effectiveness of these two strategies in controlling drug costs. The response variable is COST, the average cost of drugs per prescription per day. The data are from the mid-1990s, and are for 29 plans throughout the United States with pharmacies administered by a national insurance company. Provide a complete analysis of these data, paying particular regard to possible outliers and influential cases. Summarize your results with regard to the importance of GS and RI. In particular, can we infer that more use of GS and RI will reduce drug costs?