A pharmaceutical company wants to study the effectiveness of three different versions of a drug that treats depression. The company refers to these...

A pharmaceutical company wants to study the effectiveness of three different versions of a drug that treats depression.  The company refers to these versions as A, B and C.  A clinical study whereby patients are treated using one of the three versions is administered.  Data on drug effectiveness, age, and the version of the drug taken are collected for 36 patients.  The company wants to know whether the three versions of the drug equal in their effectiveness, and whether age influences the effectiveness of these three versions of the drug.  Accordingly, multiple regression analysis is performed for effectiveness (Y) against age, drug version and possible interactions (output is shown below).