Dr Prentice, Principal of an Elementary School, Instructs Her Teachers

Multiple Choice

Dr. Prentice, principal of an elementary school, instructs her teachers to employ a new aggression-reduction program with the second graders, and to keep using it on that group of students for the next three years. She finds that relative to the start of the program, aggression in that group of students is down 35%. This example illustrates the possibility of________ as a plausible rival hypothesis.

A) history
B) maturation
C) attrition
D) selection